teaching an endangered mammal to recognise predators

Biological Conservation 75 (1996) 51 --62 © 1995 Elsevier Science Limited

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TEACHING AN ENDANGERED MAMMAL TO RECOGNISE PREDATORS

Ian G. McLean Department of Zoology, University of Canterbury, Private Bag 4800, Christchurch 1, New Zealand

G e o f f r e y L u n d i e - J e n k i n s

Arid Zone Research Institute, Conservation Commission of the Northern Territory, PO Box 1046, Alice Springs, NT 0871, Australia

&

Peter J. Jarman

Department of Ecosystem Management, University of New England, Armidale, NSW, 2351, Australia

(Received 20 July 1994; revised version received 31 January 1995; accepted 1 February 1995)

Abstract The possibility of conditioning captive-reared animals to fear predators prior to release into the wild is often dis- cussed, but rarely attempted. Here we show that captive- reared rufous hare-wallabies Lagorchestes hirsutus, a species of marsupial that became extinct in the Aus- tralian mainland in 1991, become more cautious after conditioning to fear predators that they will encounter after release. The predators, cats and foxes, are not historical enemies of hare-wallabies, but captive-reared predator-naiVe rufous hare-wallabies reacted cautiously to them in captivity, suggesting either some genetic recognition abilities for a generalised mammalian predator, or perhaps that hare-wallabies are simply generally cautious in the presence of an unknown animal. Rufous hare-wallabies became even more cautious after two conditioning techniques were used to teach them to associate a fright with a fox or cat. We suggest that conditioning about predators may be a valuable adjunct to many management programmes involving release of predator-nai've endangered animals.

Keywords: conditioning, predators, endangered species, Lagorchestes hirsutus, hare-wallaby.

INTRODUCTION

Re-release into the wild is the ultimate objective of many programmes for captive-rearing of endangered species. Unfortunately, captive-reared animals necessarily have limited skills for survival at the release site, primarily because of lack of experience with local conditions (Box, 1991). The sources of survival skills include genetic abilities (e.g. Curio, 1975; Coss & Owings, 1978; Hirsch & Bolles, 1980; Mueller & Parker, 1980; Hobson et al., 1988) and learning (Curio et al., 1978; Regelmann & Curio, 1983; Coleman, 1987; Conover, 1987; Thornhill, 1989; Seyfarth & Cheney, 1990),

51

presumably from a mix of direct experience and cultural transmission. Currently, there is little understand- ing of the contribution of experience to survival skills, although animals such as birds and mammals clearly have complex cognitive abilities and use these to learn about their environment (Griffin, 1992).

Acclimatising animals to local habitat conditions is relatively straightforward; often some form of 'soft release' is used where animals are housed temporarily in outdoor pens at the release site (Scott & Carpenter, 1987; Kleiman, 1989). For predators, there is no obvious equivalent to acclimatisation, soft release, or feeders. In modem times, human interference has resulted in species facing entirely new kinds of predators (e.g. mammals in New Zealand - - King, 1984; a snake in Guam - - Carey, 1988). Reintroduction when the species has already failed to survive in the presence of a new predator is dearly inappropriate, unless the reintro- duced animals have survival skills that were not available to original populations, or the new predator has been controlled or eliminated. However, even if reintroduction is proposed for a site at which the predators to be faced are not new, survival may still depend to a large extent on leaming and experience (Box, 1991). Such experience may originally have been gained in a social context that is currently unavailable if all individuals are equally naive. Releases are frequently of a relatively small number of animals, and even one individual predator may be able to kill all the released animals before any have the opportunity to hone their recognition and survival skills (as has happened, Gibson et al., 1995).

Here, we describe an attempt to condition a captive- reared endangered mammal to recognise two predators that it will encounter on release into the wild. We regard the ability to deal with predators as a two-stage process (McLean & Rhodes, 1991). First, the animals must learn to recognise the predator as a dangerous object. Second, the animals must learn ways of dealing

52 L G. McLean, G. Lundie-Jenkins, P. J. Jarman

with that predator (which we term 'coping'). Each of these stages can be broken down in a variety of ways (Fanselow & Lester, 1988; McLean & Rhodes, 1991). We take the view that improved recognition abilities will give otherwise naive animals a preliminary advantage when they first encounter the predator. We have not attempted to teach coping skills, although in principle there is no reason why this should not be possible.

Study animal The rufous hare-wallaby Lagorchestes hirsutus is a small (1-0-1.6 kg), arid-zone macropod endemic to central and western Australia. About 20 species of medium-sized Australian marsupials have disappeared from the mainland in the last 50 years (Morton, 1990). The last known mainland population of rufous hare- wallabies (henceforth hare-wallabies) was destroyed by a fire and a fox Vulpes vulpes in late 1991 (Gibson et al., 1994), although the species still survives on two islands off the coast of Western Australia. Little is known about the ecology and behaviour of any hare- wallaby species. Reasons for the decline of rufous hare- wallabies are necessarily speculative, but appear to involve a mix of drought, changes in Aboriginal burn- ing practices, and the spread of introduced predators across Australia (Gibson et al., 1994). Historically, hare-wallabies were clearly associated with spinifex Triodia sp. grasslands which provided food and cover. They are entirely nocturnal, appear to be relatively soli- tary-living, and do not burrow (Lundie-Jenkins, 1989, in press). Observations both in the wild and in captivity indicate that hare-wallabies are naturally cautious (e.g. they move rapidly to cover when disturbed and are extremely watchful), will flee when approached by an enemy, and give a loud chirp that appears to be an alarm call. However, their hopping locomotion (which tends to be noisy) and use of obvious runways weaving through clumps of spinifex may make them easy prey for a sit-and-wait predator.

Rufous hare-wallabies have bred in captivity at the Conservation Commission of the Northern Territory research station, Alice Springs, Australia, since, 1981. Currently there are two captive populations of 50+ animals, one in Alice Springs and the other at a release site in the Tanami desert to the north (Gibson et al, 1994). Wild-caught animals from the extinct population noted above were added to the captive population in Alice Springs most recently in 1989. There are two release sites, both of which are subject to intensive control of feral cats and foxes. However, both these introduced predators have taken released animals during the last 2 years. Historical predators such as wedge-tailed eagles Aquila audax and dingos Canis familiaris also occur at low densities at the release sites.

METHODS

We developed two techniques for training hare-wallabies to recognise predators. In our research design we separated training about the predator and testing for

recognition skills. The design involved a series of observations investigating the response of naive captive hare- wallabies to strange objects, their ability to recognise an unknown predator, and their ability to learn recognition.

All training was conducted at Alice Springs in September and October 1992. Hare-wallabies were housed in small enclosures (15 × 7 or 10 x 7 m) with between two and four animals per pen. Food and water were provided ad libitum. All except two of the experimental animals were captive-reared and had no experience with predators; the two wild-caught animals had been in captivity for 4.5 and 10 years. All hare-wallabies were handled at least monthly during routine checks of reproductive condition and health. Vocal and olfactory communication was possible between pens, but visual barriers prevented neighbours from seeing into adjacent pens. Enclosures were provided with abundant cover in the form of clumps of spinifex and other grasses. Hare- wallabies remained in shallow depressions under dense vegetation through the day. At night, the vegetation provided cover into which animals could retreat or behind which they could conceal themselves in order to remain out of view of model predators.

Experimental animals were marked for individual recognition using human hair dye. All observations were conducted during the first 2 h from when animals first became active at dusk. Observations were made from a 3 m high platform located immediately outside the pen and close to the artificial food and water sources. However, hare-wallabies routinely fed on vegetation growing throughout the pen. Boxes and models were always placed at the front of the pen on the side away from the feeder. Observations were made under dim lighting provided by bulbs located at 5 m intervals along the roof of the pen. Lights were switched on before dusk, and were switched off when observations ceased. Binoculars were used when necessary to identify animals and record behaviours.

Animals were captured and marked, lights were turned on, and an observation platform was put in place for at least one night before observations began (usually more). While the animals were out of the pen for marking, tall vegetation within the pen was trimmed, a path for movement of the predator models was cleared, and small rocks were placed to provide a grid reference system within the pen. Some activity within the pen was required on a daily basis for adjusting lights, placing boxes, placing and removing models, and so on. In general, hare-wallabies were not disturbed by these activities and remained concealed; pens were entered daily by the keeper and the animals were accustomed to human presence. All setting up activities were conducted well before dusk.

Models were mounted on small wheeled trolleys so that they could be moved from outside the pen by pulleys or poles.

Training protocol The experimental protocol for one pen followed a stan- dard sequence over nine nights termed: Baseline (night 1),

Teaching an endangered mammal to recognise predators 53

Box (2), Model (3), Training (three events over nights 5-8), and Post-training test (9).

Baseline data were recorded from undisturbed pens. The Box (made of brown cardboard and just large enough to house the mounted fox) was introduced to document the hare-wallabies's response to a strange object. Hare-wallabies became accustomed to the box overnight and it was subsequently used to conceal model predators. A Model (fox or cat) was introduced to document the hare-wallabies's response to an unknown predator; it was pushed out of the box about 30 min before hare-wallabies became active at dusk. The model was withdrawn into the box from outside the pen at the end of the observation session and effec- tively disappeared. Training involved the model (cat or fox) that the animals in that pen had not seen during the Model test. For the Post-training test the model with which the hare-wallabies had been trained was introduced as for the Model test. Behavioural data were recorded from when animals first became active (Base- line observations), or from when they first looked at the box or model (this was invariably within a few minutes of activity beginning).

Four pens (11 animals) received a second series of training events using a different training method beginning one to eight days after the first post-training test as: Training (four events over five nights) and Post- training test (one night later).

D a t a gather ing and analys i s Three different aspects of behaviour were recorded during an observation session. Time budget data were obtained by instantaneously sampling the behaviour of each individual at 1 min intervals for about 90 rain. Recorded at the same instant were location within the pen, as the 2.5 × 3-5 m rectangle the focal animal was in; and line-of-sight between the location where the box was to be placed, the box itself, or the predator models and the focal individual (1 = in view; 0 -- hidden). 'Out of view' was recorded for the time budget sample if the animal could not be seen by the observer, but each animal's location was always known and location and line-of-sight were recorded even if the animal was out of view.

The 90 rain of data gathering represented a trade-off between gathering enough data to test for an effect, and possible habituation to the objects placed in the pen. Some individuals habituated to the models during the observation period, but many did not. The require- ments when sampling from one individual were to ensure (i) that the instantaneous samples of behaviour were reasonably independent (hence samples taken at 1 min intervals), and (ii) that enough samples were gathered to allow calculation of a time budget for each individual (hence 90 1-min samples). Any habituation to models during the tests decreased the likelihood that we would detect between-treatment (i.e. between-night) differences, making the tests more conservative.

All three observers conducted simultaneous pilot observations to standardise behavioural categories. To

further minimise between-observer bias in the data the same observer gathered all data for each pen. One observer (I.G.M.) sampled from five pens, one (G.L.-J.) sampled from two pens, and an assistant sampled from one pen.

Hare-wallabies spent most of their time feeding and watching. While foraging, they plucked or bit off vegetation (or took material from the feeders), then sat chewing the vegetation and watching at the same time. When a sample of feeding was recorded we also noted if the animal was head up (feeding-and-watching) or head down (feeding-and-not-watching). Much of the non-feeding time was also spent watching. Thus watching could be recorded either as a primary behavioural category (Watch), or as a subsidiary of a primary category (Feed). Data on the primary categories of Feeding and Watching were analysed separately; i.e. fecding- and-watching was not added into Watching.

Behavioural categories used for time budget analysis included: Feed (subdivided into: watching; not-watching; drinking); Move (subdivided into: walking - - a slow '5-legged' gait where the forelimbs and tail are alternated with the hindlimbs; running - - hopping using the hind limbs only; fast running - - very fast hopping used when startled); Watch (subdivided into postures: low - - animal on all fours or body held parallel to ground; medium - - body held at about a 45 ° angle; upright - - head above shoulders and body near verti- cal; alert - - a rare posture indicating extreme agitation where the forelimbs are held straight out from the body which is held stiff and almost erect); Investigate (subdivided into: head down, sniffing at the ground; head up, sniffing or staring fixedly at objects in the pen; for the box and models hare-wallabies were required to be within 1 m for Investigate to be recorded); a group of rare behaviours that will not be reported on here (huddle, groom, jump, interaction).

For analysis of location data, the pens were divided into four rectangles from front to back; for 10 m long pens, the rectangles were all 2.5 x 7 m; for 15 m long pens the front and rear rectangles were 2.5 x 7 m and the two middle rectangles were 5 x 7 m. All statistical analyses involved a repeated-measures design that investigated patterns of spatial use by each individual across treatment nights; thus differences in rectangle size between pens could have no effect on the patterns in the results.

No behavioural data were gathered during training events, although ad hoc observations were made. Train- ing was conducted at any time between 2030 (the approximate end of behavioural sampling) and 2300 h, or between 0430 h and dawn. Hare-wallabies have peaks in activity at these times (Lundie-Jenkins, in press). The hare-wallabies were accustomed to frequent noise and calling by animals in other pens, and always responded to such calling by looking around. The relatively infre- quent playback of alarm calls during training events was assumed to be interpreted as regular background calling by hare-wallabies in other pens, especially as neighbouring animals did not see the models (and


therefore received no conditioning) when playback occurred. A maximum of two training events (1/pen) was conducted on any night with at least 1 h between sessions.

Training involved attempts to condition hare-wallabies to associate a fright, alarm calling, or a bad experience with the model predator. Two training techniques were used, each involving two conditioning stimuli. The Walking-Model involved a model appearing suddenly from the box, 'walking' across the pen, then returning to the box (backwards); conditioning stimuli were a short series of hare-wallaby alarm calls that drew the attention of the animals to the box and model as well as warning of danger, and a loud noise as the model burst suddenly from the box. Puppet-and-Squirt involved a model operated as a puppet that leapt at hare-wallabies when they approached; conditioning stimuli were the fright associated with the leap and a short squirt from a water gun at the same instant.

The Walking-Model was attached to the far end of the pen by a pulley system. The pulley system was sprung so that the model would initially leap from the box; it leapt through a brown paper shield over the front of the box generating the loud noise. Hare-wallabies rarely give more than one alarm call at any time; we used a natural Series of three calls given over 5 s to exaggerate the warning. The model leapt from the box about 0.5 s after the first call, then walked across the pen while the second and third calls were played. The series of calls was repeated after 30 s, and signalled the return of the model to the box. Total time for a Walk- ing-Model training event was about 50 s.

For Puppet-and-Squirt, we waited until a hare- wallaby was looking directly at the model predator (and usually within 3 m), then used strings to cause the model to jump at the hare-wallaby while it was squirted with water at the same instant. The session ended either when the model had been exposed in the pen for 15 min or when all animals in the pen had been squirted at least once, whichever came first. Animals were always squirted if they approached the model, and a bold hare-wallaby could receive up to five squirts on one night while we waited for more cautious animals to approach; very cautious animals received as few as one squirt over the four nights of training.

For both training techniques the model was therefore an active stimulus for a short time, whereas during testing it was a static stimulus for a long time. For the Walking-Model we could not ensure that all animals saw the model on every training event (although most did so each time), but all would have heard the conditioning stimuli and we are confident that they would be aware of events in the pen. A major advantage of Pup- pet-and-Squirt was that we could monitor more closely both how much conditioning each animal received, and its response on successive nights. Animals that were trained using both techniques received the same model.

Data analysis involved comparing the response of each individual across treatments (Baseline, Box, Model, Post-training tests). We searched for a model

effect, indicating that hare-wallabies became cautious when model predators were in the pen, and a training effect, indicating that hare-wallabies became more cautious after training. All analyses used repeated-measure designs for complete data sets. Any variation in sample sizes is due to incomplete data. Analyses are of percent- ages or ratios and nonparametric tests were used in all cases. All tests are two-tailed unless otherwise indicated. Statistical analyses involving Puppet-and-Squirt training data used a subset of the Baseline, Box and Model test data used separately for analyses involving Walking-Model training.

Testing recognition after eight months In June, 1993, eight months after the original training experiments, three nights of observation were made on each of four pens containing l0 of the original trained animals. Group structure had not been varied for the intervening period with the exception that one female had given birth and had a dependent juvenile during the observations, and one young male had been removed from a pen containing three adults. All data were gathered by G.L.-J. as described above: observation periods were for 90 min from when animals first became active at dusk, the same behavioural samples were used for sampling, and instantaneous samples of behaviour, location and line-of-sight were recorded at 1-min intervals.

Observation nights were in the sequence: Baseline, Bilby, predator Model (cat or fox, whichever the animals had received during training). A bilby Macrotis lagotis is a small bandicoot (an omnivore), about half the size of a hare-wallaby, which is sympatric with hare-wallabies and should not be regarded as threaten- ing (although these captive-reared hare-wallabies would not have encountered a bilby). Baseline observations provided an indication of natural levels of activity and behaviour and the model bilby served as a control for the appearance of a strange animal in the pen. Models were placed into the pen before dusk at the same location as they had appeared in the earlier tests.

Statistical comparisons were made among the three nights of observation and between the Post-training test data from Walking-Model training and the response to the predator Model eight months later. All tests were on percents or ratios using non-parametric tests on repeated-measures data.

Independence of observations We were constrained to conduct all tests and observations on groups of animals for two reasons. First, the animals were part of a breeding programme for an endangered species and we were required to keep dis- turbance to a minimum. Second, most of the animals had lived in small groups for their entire lives, and may have been unacceptably stressed if placed alone in a pen (although this was not tested). As we indicate in the sections on spacing behaviour, dominance and avoidance behaviours influenced use of space; i.e. movements within the pens were not independent.


Statistical analyses of individual behavioural responses were therefore potentially compromised by within- group correlated responses. We address this issue in some detail because it is likely to be a frequent problem in studies of endangered species.

The problem to be resolved involves distinguishing whether responses of individuals are directly to a treatment (in this case, a model or box), or are responses to other individuals that are responding to the treatment. In the former situation, all individuals are responding independently and it does not matter that they lived in a group at the time data were collected. In the latter situation behaviours of within-group individuals are linked and the true independent measure is the response of the group. We tested for independence in two ways. Both involved comparing within- and between- group variation in behaviour. Independence is supported if the two measures of variation are similar.

(1) We made within- and between-group comparisons within one treatment using each instantaneous behavioural sample taken during the 90 min of observation. We call this behavioural similarity. We randomly paired a focal animal with two other individuals, one within its pen and the other from another pen. Each sample for the focal individual was matched with the sample taken at the same time for the within-pen animal, or at the equivalent time (determined by when both animals first sighted the model) for the between- pen animal. Thus a sample of behaviour taken 10 min after the focal animal first saw the model was matched with the sample taken during the same minute for the within-pen animal (who must also have seen the model for the comparison to be made), and also with the sample taken I0 min after the between-pen animal first saw the model (between-pen observations would usually have been made on different nights). Matching was conducted for the first 40 samples available for a pair where both animals were in view (i.e. if one or both animals were out of view for that instantaneous sample, the match of behaviours was discounted), and we determined the proportion of matches of behaviour that were the same. Thus for each focal animal we measured behavioural similarity at equivalent instants in time with respect to first sighting of the model, to a within-pen animal and to a between-pen animal. A significantly higher within-pen mean indicates that within- pen behaviour was more linked than between-pen behaviour, and supports the conclusion that behaviour of within-pen animals was linked. Lack of significance indicates that within-pen behaviours were no more linked than between-pen behaviours and suggests independence.

We used 12 focal animals from the eight pens (pens with two animals provided one focal animal, pens with three animals provided two focal animals, the two dependent juveniles were rejected because they tended to remain out of view for long periods). Focal animals were chosen randomly and were paired with randomly chosen individuals from within- and between-groups.

Reciprocal pairings, where the same data would be used twice, were disallowed. In each of the four pens with three animals, one animal was used twice although its roles were determined randomly. An individual was only used once as the match for a between-group pair- ing; however, six animals served as both a focal animal and a between-group animal, and six animals served as both a within-group and between-group animal. Sam- ple sizes were too small to allow an effective test under the most rigorous design where an animal was used once only in any of the three roles.

(2) Kenny and La Vole (1985) have developed a method of testing for individual- and group-level correlations in research designs similar to the one used here. This method calculates a measure called the intraclass correlation using within- and between-group mean squares, calculated using ANOVA procedures. Within- group independence is indicated as the correlation coefficient approaches zero, linked within-group behaviour is indicated as the correlation coefficient approaches + 1 (within-group behaviour is less variable than between-group behaviour), and linked between- group behaviour is indicated as the correlation coefficient approaches -1 (within-group behaviour is more variable than between-group behaviour). Measures used to make the calculations are individual scores; in the hare-wallabies study we used time budget measures for each behaviour. Unfortunately, this method is limited in application to hare-wallabies because the test was designed for humans giving a response to a question (e.g. the attitudes of a husband and wife may be more similar than the attitudes of randomly chosen members of a community). Strictly, the comparable responses of hare-wallabies would be one instantaneous sample taken at equivalent times for each individual, because this is the sampling level at which the question of independence needs to be addressed. It is quite possible for two animals to spend similar proportions of time doing a behaviour, but for them to have behaved independently (e.g. they both Watched for 20% of the time, but rarely Watched at the same instant). Thus a result from this analysis suggesting that within-group behaviours were linked (i.e. not independent) still needs to be checked using the first test described above. How- ever, reasonable confidence can be placed in a result indicating independence.

Both of these tests require a non-significant result for the conclusion to be drawn that animals were behaving independently. We therefore used p = 0.25 to determine significance instead of the more usual p = 0.05, as recommended by Kenny and La Vole (1985).

RESULTS

General Observations were recorded from 22 hare-wallabies (15 females, seven males; including two young-at-foot, i.e. mobile young that occasionally suckle but are no longer

56 I.G. McLean, G. Lundie-Jenkins, P. J. Jarman

Table 1. Intraelass correlations (ICC, Kcony & La Voie, 1985) for three behavioers (LOS, line-of-sight) sampled during recognition tests (MD, Model test; PT, Post-training test) in which model and training effects were most likely to be found, for hare-wallabies subjected to conditioning experiments on

predator recognition

Behaviour Test ICC p

LoS MD 0.30 0.27 PT 0.30 0.27

Watch MD -0-37 0.09* PT -0.17 0.45

Feed MD -0.17 0.45 PT -0.10 0,6

*Significance accepted at p < 0-25.

carried in the pouch) in eight pens for the Walking- Model, and 11 hare-wallabies in four pens for Puppet- and-Squirt. Four pens each received the cat and fox for the Model tests, and therefore the fox and cat for training. When undisturbed (i.e. Baseline observations), hare-wallabies spent 44% of their time feeding and drinking, 25% of their time watching and 19% moving (out-of-view observations were removed from the total time budget for these calculations). All other behaviours in the time budget were rare.

No difference in response was found to the cat and the fox, and responses to the two models are lumped. No differences in model or training responses were found between males and females. Young animals (either young-at-foot or recently weaned juveniles) appeared to be somewhat more variable in behaviour than adults, but numbers were too small (n = 4) for this variation to be tested statistically. Some young animals spent almost all their time feeding; others disappeared for long periods whether or not there were models in the pen, apparently to sleep. Young animals were generally subordinate to other hare-wallabies and some of their behaviour patterns (especially spacing) were clearly determined by social dynamics within the pen.

Responses to the box and models were quite variable: some animals moved to the back of the pen but did not adjust their time budget, some animals remained out of line-of-sight of the models (and some- times out of view of us as well), and some animals became more watchful but did not adjust their use of space. These between-individual differences in patterns of behaviour decreased the probability of significant effects being detected and made the analysis more conservative.

Some animals were clearly cautious throughout the series of tests, whereas others were bold, frequently approaching and investigating the box and models. Any initial caution when the box was first seen usually extinguished within a few minutes, whereas initial caution during the Model test declined more slowly, with some individuals remaining cautious throughout the 90-min test. The effect of the two training techniques varied across individuals, with some animals showing no response to the Walking-Model (WM), but a strong

response to Puppet-and-Squirt (PS), and others showing similar responses to the two techniques. Visual inspection of the data for each individual indicated that only one animal (a young male, No. 322) clearly became less cautious through the series of treatments ending in WM training (by moving forward in the pen, feeding more and watching less), although several others showed little variation in response. Number 322 responded dramatically to PS training by moving to the back of the pen, becoming watchful and feeding little.

A strong model effect was found throughout the data. A training effect was found in only some analyses and data are presented in the order that highlights the training effect. No statistical differences between the WM and PS training techniques were found for any variable (results not presented).

INDEPENDENCE

Observations on wild hare-wallabies are limited, but suggest that these are not highly social group-living animals (Lundie-Jenkins, unpublished data). Our subjective impression of hare-wallabies in the pens was that they did not behave as members of a cohesive group such as a flock of birds would, although clearly the pen imposed restrictions on their ability to function independently. In general, they tended to avoid or ignore each other.

Behavioural similarity (the first test of independence outlined in Methods) was tested using data from Post- training tests and Model tests (these are the tests in which within-group behaviour was most likely to be linked). For the 40 matched behaviours, numbers of similar behaviours were (within-group:between-group, X + SE) 7.2 _+ 1.0:6.3 + 0.7 for Post-training tests and 6.2 +_ 0.9:6.1 +_ 0.6 for Model tests. The differences were not significant (paired t-tests, t = 0.9, p = 0.39 and t = -0.1, p = 0.9 respectively) suggesting that within- and between-group behaviour had similar levels of similarity (i.e. within-group behaviour was independent).

We calculated the intraclass correlations (the second test of independence) for data from Model and Post- training tests for line-of-sight, Watch and Feed (the latter behaviours were the most frequent in the time budget data, and were the behaviours most likely to give training effects, see below). Of the six intraclass correlations calculated, two were positive but not significant and four were negative (i.e. in the wrong direction if within-group behaviour was linked, Table 1). One negative coefficient was significant (i.e. p<0.25), indicating that between-group variation was lower than within-group variation. These results do not support the hypothesis that within-group behaviour was linked.

We conclude that hare-wallabies behaved independently in the pens with respect to our behavioural measures, and in the following analyses treat the data from each individual as a separate measure of response.

Line-of-sight A significant increase in proportion of time spent out of view of the models was found for both training tech-


45

35

o

25 O

15

b

[ ] W M N = I 6

SS

45

.o_ ~. 35

O 25

15 Base Box Model Post-test

Treatment

Fig. 1. Proportion of time (X + SE) hare-wallabies were out of line-of-sight with the location at which the box or models were placed during four treatment conditions. BASE, Base- line observations; POST-TEST, Post-training test (WM,

Walking-Model; PS, Puppet-and-Squirt).

niques (WM: Friedman's statistic = 10-25, p = 0.02, n = 16; PS: Friedman's -- 9.44, p = 0.02, n -- 11; Fig. 1). The increases between Model and Post-training tests were significant (Wilcoxon tests, WM: 1-tailed p = 0.04; PS: 1-tailed p = 0.03). These results indicate both a model effect, with the animals becoming increasingly cautious as the box and models were introduced to the pen, and a training effect, with animals becoming even more cautious after training. The reduced sample size for WM training is because line-of-sight was not recorded in all nightly observations of the first two pens studied.

l eed lg A significant decrease in time spent feeding and drinking was found for both training techniques (WM: Friedman's = 15.71, p = 0.001, n = 22; PS: Friedman's = 9.77, p = 0.02, n = 11; Table 2). There were no significant differences between the Model and Post-training tests for either training technique (Wilcoxon tests, p > 0-1). These results indicate a model effect, with the animals feeding and drinking less when models appeared in the pens, but no training effect.

We subdivided the feeding data by calculating the ratio of watching/(not watching+drinking) for each individual in each treatment condition. During behavioural sampling we had only recorded 'feeding and watching' if the animal was clearly looking around while chewing; thus the proportion of feeding time spent looking around should be an indication of how watchful the animal was. Animals that were drinking looked at the water tap and did not look around. Significant variation was found for amount of time spent watching while feeding for both training techniques (WM: Friedman's statistic = 11.79, p = 0.008, n = 22; PS: Friedman's = 9.06, p -- 0.03, n = 11, Fig. 2). These results were due primarily to an unexpected decrease in the ratio from Baseline to Box. It appeared that some animals were not entirely habituated to the observers on the first night of observations, although they were clearly habituated on subsequent nights. We therefore draw no conclusions about model effects. However, a significant training effect was found in the ratio when Model and Post-training tests were com- pared (WM: Wilcoxon test, p -- 0.005, Sign test, p = 0.03, n -- 22; PS: Wilcoxon p -- 0.008, n = 11). We conclude that feeding hare-wallabies became more watchful after training about an unknown predator.

Watching A significant increase in time spent watching (incorporating all four watching postures) was found for the Walking-Model (Friedman's statistic = 20-02, p = 0.0002, n -- 22, Table 2), but not for Puppet-and-Squirt (Friedman's = 7.15, p -- 0.07, n = 11, Table 2). How- ever, as for feeding, no significant difference was found

Time budget All out-of-view observations were removed from time budget data before percentage of time spent in each behaviour was calculated. Thus the sample size for each animal varied considerably (Baseline: X = 77.5, range = 34-106; Box: X = 81-8, range = 45-99; Model: X -- 78, range = 42-96; WM: X = 78.0, range 54-91; PS: X = 71.6, range = 17-87). No analysis of proportion of time spent out of view is presented because those data are included in line-of-sight observations (any animal out of view for us was always out of line-of-sight of the models). We predicted that hare-wallabies would spend less time feeding and more time watching during the series of treatments. We made no prediction for amount of time spent moving.

Table 2. Time budget of hare-wallabies living in pens during five treatments, presented as mean% (SE) of total observations,

excluding out-of-view observations WM, Walking-Model post-training test; PS, Puppet-and- Squirt post-training test. N = 22 animals for all treatments except PS where n -- 11. Note that all statistical tests reported in the text were a repeated measures design on complete data sets; tests incorporating PS data were on a subset of the

presented data for the other treatments.

Feed + drink Watch Move

Baseline 44.4 (4.01) 25-1 (2.65) 19-0 (2.40) Box 46-7 (3.77) 23.5 (2.47) 21.5 (2.46) Model 34.0 (4.20) 34.3 (2.68) 18.3 (2.31) WM 35.1 (4-21) 33-0 (2.77) 19.7 (3.12) PS 27.9 (4.12) 34.2 (3.98) 22.6 (3.59)


0.6

0.5

0.4 0

0.3

0.2

0.1

[ ] F e e d W M N = 2 2 11 F.2 A [ ] Watch WM N = 22

1 0.7

0.6

0.5 .,q

0.4

0.3

0.2

0.1

118 6 Watch PS N = 11

1.4 ~ ~ ~ 1.2

1,0

0.8

0.6

0.4 Base Box Model Post-test Base Box Model Post-test

Treatment Treatment

Fig. 2. Watchfulness within the time budget of hare-wallabies during four treatment conditions. See text for definitions of Ratios. BASE, Baseline observations; POST-TEST, Post-training test (WM, Walking-Model; PS, Puppet-and-Squirt).

between Model and Post-training tests. These data indicate a model effect, but no training effect.

When orienting specifically towards the models, hare-wallabies tended to use either low or upright postures, whereas when just looking around they tended to use the medium posture, although they also watched the models using the medium posture. Within the Watch data we calculated a ratio based on postures used specifically to watch the model divided by the posture used to watch more generally. Investigate/head up, a behaviour that involved orienting specifically towards the model but at such close range that the animal should be regarded as curious rather than fearful, was combined with the medium posture to generate the ratio: (low+upright+alert)/(medium+investigate/head up). A model effect is evident in this ratio (Fig. 2), although it was only significant for Walking-Model training (WM: Friedman's=13.58, p -- 0-004, n = 22; PS: Fried- man's = 5.29, p = 0.15, n = 11). Despite the similarity of the means, a weak training effect was found for the Walking-Model (Wilcoxon test, p = NS; Sign test, p = 0.04, n -- 22; medians were Baseline = 0.47, Box = 0.42, Model = 0.56, WM -- 0.94, PS -- 0.76).

Moving Hare-wallabies spent similar amounts of time moving (walk+run) during all treatments (Table 2). No significant variation was found for either training technique (Friedman's tests, p > 0-1).

Location We predicted that hare-wallabies would tend to move away from the front (where the box and models were placed) through the series of treatments. The animals tended to spend most time in either the front or the

rear of the pens. However, in part because of the effects of dominance on spatial distribution noted above, we found that some animals moved to the mid-rear sector,

40

30

20

"-" 10 t-

50 == V

40

30

Base Box Model Post

• PS front

20

I0

Base Box Model Post

Treatment

Fig. 3. Use of pens by hare-wallabies during four treatment conditions for two training techniques (WM, Walking-Model, PS, Puppet-and-Squirt). Data are for the front and mid-front quarters of the pen and the rear half divided by two. BASE,

Baseline observations; POST, Post-training test.


Table 3. Mesa% (se) time budget and rstio dsta for nffom hare- wsUM3ies tested for recognition of a non-threstenln~ model (biiby) sad a predator model, eight months after training about the predator ( p o s t ~ response from eight months earlier

indicated by Post-test Line-of-sight was calculated as the percentage of total observations for each treatment (see Methods). Feed and Watch data were calculated as the percentage of the total time budget from each treatment, with out of view observations removed from the total. Formulae for calculation of ratios are described in Results. N -- 10 in all cases.

Line of Feed + Watch Feed Watch sight drink ratio ratio

Baseline 39.3 (3.6) 39-6 (4.5) 36-1 (4-5) 0.26 (0.05) 0-35 (0.07) Bilby 39.9 (3.7) 36.5 (3.9) 40.9 (4.0) 0.29 (0-06) 0.25 (0-06) Predator

model 41-6 (4-2) 41.4 (5-5) 35-8 (4.6) 0.31 (0.08) 0-31 (0-04) Post-test 40.5 (5.7) 28.8 (5.5) 32-1 (4.5) 0.45 (0.11) 1.42 (0.50)

immediately behind the midline of the pen. We therefore combined the two rear rectangles by adding the percent of time spent in each and dividing by two for each individual.

Use of the pen in relation to treatment is shown in Fig. 3. Hare-wallabies used the two front sectors of the pen significantly less through the series of treatments (very front of pen, where feeder and model were placed: WM: Friedman's statistic = 13.8, p = 0.003, n = 22; PS: Friedman's = 10.10, p = 0.02, n = 11; mid-front sector, immediately forward of the midline: WM: Friedman's = 9-491, p = 0-02; PS: Friedman's = 3.393, NS). Use of the rear of the pen increased, although not quite significantly (WM: Friedman's -- 7-803, p -- 0.0503; PS: Friedmans = 7-691, p = 0-0529).

The above results indicate a model effect. However, no training effect was found in the location data, possibly because the model effect was so strong that the already low use of the front in the Model test (22.7%, Fig. 3) represents a ceiling effect. Animals were presumably hungry when we were sampling as they had not eaten for at least 13 h, and may have been forced to spend at least a small amount of time at the feeders in the front. In all of the tests, only two animals (both females) spent no time in the front at the feeder (No. 228 for the Model and WM tests, and No. 221 for the Model test).

Recognition after eight months For comparisons between the Post-training test and the Model test eight months later, recognition of the model is implied if no significant differences are found. None was found for line-of-sight, Feed or Watch (Table 3), providing weak support for recognition. However, a significant effect was found for the Watch ratio (hare- wallabies became less watchful after eight months, Wilcoxon test, p = 0.006) and the Feed ratio approached significance (hare-wallabies watched less while feeding after eight months, Wilcoxon, p = 0.08), suggesting that hare-wallabies did not recognise the predator model.

For comparisons among the three consecutive nights of observation done after eight months, none of the measures that had shown a training effect in the earlier data varied significantly (i.e. line-of-sight, Feed-and- Watch ratio, Watch ratio; all comparisons were Fried- man's tests; Table 3). Use of space also did not vary significantly among the three nights of observation (Friedman's tests, data not presented).

Overall, these results suggest that after eight months hare-wallabies did not recognise the model with which they had been trained.

DISCUSSION

Hare-wallabies raised in pens were initially cautious when presented with a strange object (the box), but they were even more cautious when presented with a model predator of species never encountered in evolutionary time. This surprising result suggests some genetic ability to recognise entirely new predators. However, hare-wallabies were presumably the prey of several predators that are rather similar in appearance to cats and foxes, including the thylacine Thylacinus cynocephalus, the western native cat Dasyurus geoffroii, and dingos in the last few millenia. Although the data can be interpreted as indicating some form of genetic recognition ability for a generalised mammalian predator, a simpler interpretation is also available. As naturally cautious animals, hare-wallabies may react even more cautiously to an animal larger than themselves than they do to an inanimate strange object.

From a conservation perspective, a cautious response in the face of an unknown predator clearly has survival value for animals re-introduced to the wild. Our data suggest that captive-reared hare-wallabies can be trained to become even more cautious when faced with a new predator. After training about cats and foxes, hare-wallabies were more likely to hide from the predators, and watched them more. These responses were the most likely to be found in a pen situation and we con- sider them to provide strong support for the effective- ness of the conditioning techniques.

Five aspects make the statistical analyses of the training result extremely conservative:

(1) because the pens were small, animals had limited response options (for example, they could not simply run away);

(2) several response options were available and doing one (e.g. hiding) could result in no change in another or even move it in the opposite to the predicted direction (e.g. the proportion of time feeding could appear to increase because an animal spent most of its time out of view of the observers);

(3) animals could adjust their response within a general behaviour (as they did with feeding and watching) in ways that we could not detect using our sampling methodology;

(4) social dynamics within the pen could force an appar- ent response in the opposite to the predicted direction;


(5) some animals clearly habituated to the models during the 90 min test and an initial training response may have been extinguished.

These five factors add variance to the data that decreases the chance of finding statistical effects, as behaviours were analysed separately and no animals were excluded from any analysis. Balanced against them is the possibility that behaviour of animals within pens was linked due to non-independence of responses, resulting in inflated sample sizes (although we have shown the problem does not arise in this study).

Our data on the response of hare-wallabies to predator models after eight months must be interpreted cautiously, due to the small sample size. However, the data do not suggest that hare-wallabies retained any memory of the model, suggesting that the conditioning may only be effective for a short time. Young ferrets Mustela eversmanni retain some memory of a predator that they have been conditioned to fear for one month (Miller et al., 1990). Clearly, the length of time that memory of a predator lasts in the absence of further experience with that predator requires more research.

Many animals adjust their behaviour in the presence of predators (review in Elgar, 1989), and some follow initial caution or escape behaviour with curiosity and investigation to the extent that they may approach closer than the distance at which they initially fled (Walther, 1969; Pitcher et al., 1986). Such curiosity presumably has survival value in that the animals learn about the predator, and can monitor its location and behaviour while retaining the ability to escape (Griffin, 1992). Animals raised in captivity may tend to become less cautious or curious about new stimuli, there may be critical periods for learning, or the artificial environment might not provide the social context in which the animals routinely learn in the wild (Kleiman, 1989). In our view, solutions to these problems must include imaginative programmes designed to condition animals to respond in appropriate ways to the problems they will face in the reintroduction environment (for more general comments in a similar vein, see Soul6, 1990). For animals with complex cognitive abilities, such as birds and mammals, the likelihood that conditioning will be effective in adjusting the behaviour of the sub- jects may depend more on the skills of the researchers than on the developmental limitations imposed by captive-rearing.

We emphasise that in this study, testing for improved recognition skills, and training, were separated. Also, our testing technique tended to extinguish the conditioning of recognition skills. In a management programme, testing might not be a regular component of training, except possibly where such data can be gathered during training as was feasible in our second training technique. Of course, if individual animals are extremely variable in response or respond variably to different training techniques, it may be necessary to test each individual prior to release.

The study described here represents only the first step of a programme designed to condition hare- wallabies (or any animal) to develop predator-coping skills. There are a number of difficult questions that the study does not address, but we use it to raise the questions and make some comment (also see McLean et al., 1995). First, we taught recognition skills by conditioning animals to associate a fright with a model predator; the hare-wallabies themselves determined how they would respond. We do not know what the most appropriate responses by hare-wallabies would be to a real cat or a fox in the wild, although it should be possible to teach hare-wallabies those responses. Sec- ond, we do not know if the recognition skills that we can give hare-wallabies will make any difference to survival. Of the few studies that have addressed this question, one found that trained animals survived better (Ellis et al., 1977), one found no effect (Miller et al., 1990, 1994) and two that we have conducted found no effect (McLean & Hoelzer unpublished data, Adams, Hume and McLean, unpublished data), although our sample sizes are still too small for an effective test. Third, any recognition skills that hare- wallabies acquire through conditioning are likely to wane over time. Currently, predators occur erratically at the release sites due to the combination of an effective but costly control programme, and the extreme conditions there which must approach the limits of tolerance for cats and foxes. For the conditioning to be reinforced, and to ensure that hare-wallabies learn about cats and foxes, it may be necessary to cease or reduce predator control. Although reduced predator control may be desirable economically and experimen- tally, it is not at all clear what density of predators would be acceptable, or what proportion of hare- wallabies should be preyed upon before the experiment is considered either a success or a failure.

Could training about predator-recognition be an effective management tool in conservation biology? Reintroduction techniques are currently being developed for many species that have been raised in an impoverished environment (e.g. captivity, an island). Attempts have been made to condition animals to search for and process wild foods, behave in ways that minimise encounters with predators, or use applopriate home sites (these and other examples are reviewed in Olney et al., 1994). We believe that conditioning animals to fear predators is just another tool that should be used as needed in reintroduction programmes. We are frequently told that it is 'too expensive', 'too difficult', or the complaint is made that it is not known to 'work' (i.e. predator-trained individuals are not known to survive better). We can only address these comments succinctly here. Predator-training can be done quickly; most of the cost is in setting up and testing of techniques. The cost in both money and time should be small once a training programme has been developed. The question of whether training 'works' becomes less of an issue if overall costs are kept low. However, we note that showing training works for a monkey does


not mean that training will work for a wallaby. Although it might be possible to conduct preliminary tests on closely related species that are more abundant, ultimately the test must be performed on the species of interest. An element of faith will almost certainly be required.

ACKNOWLEDGEMENTS

We thank K. Bellchambers, D, Bryan, N. De Preu, J. Lundie-Jenkins, G. Mckenzie, D. Wurst and especially L. Kean for assistance. S. Green made the stuffed fox. The hare-wallaby breeding programme was initiated and is managed by Ken Johnson. We thank all staff of the Conservation Commission (Alice Springs) for discussion and logistic support, and C. Hoelzer and B. Miller for comments that greatly improved the manuscript. G. Fletcher directed us to the work by Kenny and La Voie and G. Rhodes assisted with the analysis. The hare-wallaby programme is supported by World Wide Fund for Nature (Australia), the National Estate Grants-in-aid programme, the Endangered Species Programme of the Australian National Parks and Wildlife Service, and the Conservation Commis- sion of the Northern Territory. Funding for IGM was provided by the University of Canterbury.

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teaching an endangered mammal to recognise predators

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