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United States Department of the Interior

FISH AND WILDLIFE SERVICE

Kodiak National Wildlife Refuge 1390 Buskin River Road

Kodiak, Alaska 99615 (907) 487-2600

September 28, 2011

Memorandum

To: Gary Wheeler, Refuge Manager

From: McCrea Cobb, Wildlife Biologist

Subject: Results of 2011 aerial survey of mountain goats on Kodiak Island, Alaska.

SUMMARY

Biologists from the Kodiak National Wildlife Refuge (KNWR) and Alaska Department of Fish

and Game (ADF&G) surveyed for mountain goats on Kodiak Island in July and August, 2011.

We counted a total of 2,348 goats, for an island-wide population estimate of 2,400 to 2,600

goats. We counted 399 kids (20 kids: 100 adult). Adequate weather conditions during the 9

survey days (overcast to sunny with wind speeds <10 knots) allowed us to survey alpine habitats

in all 8 ADF&G mountain goat Hunt Areas. Our survey results were consistent with previous

surveys in hunt areas along the northern road system and central portions of Kodiak, suggesting

stable populations in these regions. However, our counts were higher than previous counts in the

southern portions of Kodiak Island, specifically in south end of Hunt Area 480, suggesting that

numbers continue to increase in these areas. Given the continued increasing abundance of

mountain goats on Kodiak, I recommend that Refuge and ADF&G biologists develop a more

cost-effective and logistically-feasible approach to monitoring mountain goat abundances.

Possible methods include population indices based on annually surveyed subpopulations and a

qualified estimate of mountain goat sightability to allow for confidence intervals.

BACKGROUND

Eighteen mountain goats (7 males and 11 females) were introduced to the Hidden Basin region

of Kodiak Island, from the Kenai Peninsula, in 1952 and 1953. By 1964, the population reached

26 animals. The first hunting season was authorized in 1968 when the population was estimated

to be at least 71 animals. Goats were lightly harvested initially because of a restrictive draw hunt

and limited areas that were open for hunting. The population increased through the 1980’s from

150 to over 400 animals. Permits changed from a draw hunt to a registration hunt in 1984 and

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1985, but resulted in high hunter densities, less harvest selectivity, “herd shooting”, and wanton

waste (Smith 1986). Drawing system regulations were reestablished the following year, and

remained in place throughout the 1990s. The mountain goat population continued to grow

throughout the 1990s, and ADF&G responded by opening new areas on Kodiak to hunting.

Hunting permits were issued for the first time in the southern portion of Kodiak in 1991, and a

new hunt area close to the road system was opened in 1995. By 1999, the population increased

to an estimated 1,000 animals, and goats were believed to occupy all available habitats on the

island. Hunt areas encompassed all of Kodiak and Uganik Islands in 2001, and a new hunt area

in the northern portion of the road system was opened. In 2001, the Kodiak-Aleutian Regional

Advisory Council (KARAC) received a proposal to include Kodiak mountain goats as a

federally-listed subsistence resource, and to open Federal lands to subsistence hunting by permit.

A joint (Kodiak Fish and Game Advisory Committee and KARAC) working group formed to

discuss ways to meet subsistence needs of rural residents, while retaining state harvest

management. The Board of Game approved a proposal from the working group to increase the

maximum number of drawing permits from 250 to 500 and establish registration hunts after the

drawing hunts, if allowable surpluses of goats exist. This regulatory change halted efforts by the

Federal Subsistence Board to create a subsistence mountain goat hunt. In 2009, the state of

Alaska approved more aggressive harvest management measures (registration hunt) in a segment

of the population receiving lower hunting pressure (Hunt Area 480) because of limited floatplane

accessibility. The population was estimated to be approximately 2,500 animals in 2010

(ADF&G, unpublished data).

Surveys of mountain goat abundance have been conducted annually by the ADF&G and KNWR

biologists since 1975. Although survey effort has varied over the years, from island-wide counts

to partial surveys, results provide baseline data on historical goat population growth, kid

recruitment, and range expansion. The logistics of surveying goats has been increasingly

difficult as the population has expanded in range and abundance. Marginal flying conditions and

limited budgets have been the primary reasons that island-wide surveys have been irregular.

Mountain goat aerial surveys require high cloud ceilings and low wind speeds, which are unusual

conditions on Kodiak. Given these challenges and the potential for further population increases,

a more statistically robust and logistically feasible method to quantify goat trends or abundance

is needed.

STUDY AREA AND METHODS

Surveys were conducted from an Aviat Husky aircraft piloted by Isaac Bedingfield (KNWR) and

carrying McCrea Cobb or Bill Pyle (KNWR) as the passenger (Hunt Area 480), or a Cessna O-1

Bird Dog piloted by Doug Hilty and carrying John Crye (ADF&G) as the passenger (other Hunt

Areas). Both the pilot and passenger acted as observers during surveys. We focused survey

efforts in grass and forage-dominated alpine habitats above shrub-line that were within

established ADF&G mountain goat hunt areas. The KNWR pilot attempted to remain at or

around 150 m (500 ft) above ground level while surveying, which was a balance between being

able to identify mountain goats and having a wide enough field of view from either side of the

aircraft. Upon encountering a mountain goat group, observers tallied the group size and number

of kids, and recorded a GPS waypoint. Mountain goats were considered an individual group if

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they were separated by >500 m from other goats, and behaviorally responded to observers in a

cohesive manner.

I entered mountain goat group waypoints and the track of the survey planes into a GIS for data

storage and analysis. Because of the narrow terrain, it was often not feasible or efficient to fly

directly over goat groups while recording GPS waypoints. In those conditions I manually

adjusted the locations of some waypoints to better reflect their actual locations using ArcMap 9.3

(ESRI, Redlands, CA).

RESULTS

We surveyed for 21 hours over 9 survey days (July 19 and 28; and August 6, 8, 10 – 12, 16, and

17) (Figure 1). We counted a total of 2,348 mountain goats in 319 groups (Figure 2, Table 1).

The mean group size was 7 goats (SE = 0.55), and group sizes ranged from 1 to 79 goats. Based

on these survey results, the 2011 population estimate was 2,400 – 2,600 goats. This is the

highest mountain goat count and population estimate ever recorded for Kodiak Island. The

mountain goat population was estimated at approximately 2,300 goats in 2010, and the highest

previous island-wide count was 1,975 goats (2008).

The mountain goat population has exhibited exponential-like growth (p < 0.05, R2 = 0.98) since

their introduction (Figure 3). However, population growth among hunt areas has varied over

time. Areas near the initial introduction site (Hunt Areas 472 and 473) appear to have peaked in

abundance in the 1980s and 1990s and subsequently have stabilized at lower abundances (Figure

4). Along the road system (Hunt Areas 478 and 479), goats rapidly increased in abundances in

the mid-1990s and have been relatively stable at higher abundances. Within KNWR (Hunt

Areas 474 and 480), mountain goats have exhibited the rapid growth over the past 10 years.

Currently, Hunt Area 480 holds 62% of all goats surveyed (Figure 5).

We counted 399 kids (20 kids: 100 adults). Kid: adult ratios were lower this year than the

previous 10-year average (23 kids: 100 adults); however a consistent trend over time during this

period was not apparent (Table 2). Adult: kid ratios varied between hunt areas from 0 kids: 100

adults (Hunt Area 472) to 26 kids: 100 adults (Hunt Area 478). Although kid: adult ratios in

Hunt Area 472 historical have been below average ( 10 year = 18) and the population has been

consistently small, the absence of kids this year within this hunt area is notable.

DISCUSSION

The Kodiak Island mountain goat population continues to increase in size and range. Although

the northern and centrally located subpopulations appear to have stabilized or declined,

subpopulation sizes on the southern ranges, particularly in the KNWR (hunt area 480), have

increased. Continued increases in goat abundances have prompted concerns by KNWR

biologists over potential impacts to alpine flora and fauna. High densities of ungulates can cause

adverse ecological impacts (Hobbs 1996), but the relationship between Kodiak goat densities and

their effects on vegetation is unclear. Introduced ungulate populations often follow a general

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trend of rapidly increasing to peak abundances, crashing to low levels, and then increasing to a

theoretical carrying capacity below peak abundance (Caughley 1970). During the initial growth

phase, ungulates can cause detrimental landscape-level effects by altering vegetation structure

and composition, soil system functioning, and chemical processes (Hobbs 1996, Spear and

Chown 2009). Empirically-driven harvest management can successfully slow irruptive

population growth rates, resulting in less natural resource damage and an elevated long-term

ecological carrying capacity (i.e. more harvest opportunities in the long-term). Hunter harvests

offer a potential tool in regulating Kodiak’s mountain goat population sizes, but currently the

relationship between harvests and annual changes in population abundance is unclear.

Quantifying the effects of hunter harvest on annual changes in population size is needed to

maintain a viable mountain goat population that limits impacts to Refuge resources while

providing an opportunity for hunter harvest.

In 2010, a mountain goat registration hunt was opened in a portion of KNWR (Hunt Area 480) to

encourage higher harvest levels. Although it is still too early to make to conclude whether this

regulatory change has had the desired effect, it is worth reviewing potential additional measures

if the goat population continues to increase in this region. It has become increasingly apparent to

KNWR biologists that a lack of access options might be a primary barrier to higher goat harvests

in Hunt Area 480. Hunters generally access remote regions in float planes landing on alpine

lakes. However, there are a limited number of lakes large enough to land on in hunt area 480, so

goat hunters must hike long distances to reach goat habitats. A potential solution would be to

encourage air charters to utilize wheeled aircraft that have the ability to land on alpine meadows

and ridge tops. Secondly, additional regulatory changes may need to be considered. Examples

include not counting goats harvested in Hunt Area 480 toward a hunter’s bag limit, and

extending the season within Hunt Area 480.

Although we estimated that the current mountain goat population is 2,400 to 2,600 goats, based

on 2,364 goats counted during surveys, there are a number of limitations associated with this

estimate worth mentioning. We conducted surveys only in alpine terrain, so mountain goats

occupying lower elevation habitat and outside of the survey range were not counted. The

abundance of this segment of the population was unknown, but we assumed it was small (>100

goats). Additionally, a statistically-robust estimate of goat sightability was not quantified.

Sightability likely varied across Kodiak, influenced by habitat characteristics and goat habitat

use patterns. Observers noted that goats were more difficult to spot on granite than other

substrates, and granite cliffs were often associated with smaller boulders, which further limited

observer sightability. These habitats were common in the northern portion of Hunt Area 480,

and Hunt Areas 476 and 474. Goat sightability was likely lower in these areas compared to other

parts of Kodiak, but this was not reflected in the current population estimate.

Kid: adult ratios from our surveys (20 kids: 100 adults) were comparable to more well-

established and native mountain goat populations in Alaska. Between 2003 and 2007, kid: adult

ratios on the Kenai Peninsula ranged from 21 to 27 kids: 100 adults (McDonough 2008). In the

Ketchikan area, kid: adult ratios averaged 27 kids: 100 adults from 1996 to 2006, ranging from

17 to 39 kids: 100 adults (Porter 2008). Mountain goat populations in the southeast Alaska

mainland averaged 27 kids: 100 adults between 1996 and 2006 (Lowell 2008).

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To improve survey results, future efforts should be focused on developing a quantitative estimate

of goat sightability that can be applied to count data. Biologists plan to develop a methodology

that would allow for robust confidence interval estimates. Field and statistical methods for

determining sightability and confidence intervals have greatly improved since these surveys were

initiated (Seber 1992), and these methods have been successfully applied to population estimates

of mountain goats and Dall’s sheep (Udevitz et al. 2006, Rice et al. 2009). Conducting island-

wide population counts of Kodiak Island mountain goats has become increasingly costly to

achieve because of the increasing size and range of this mountain goat population. Completing

island-wide counts is also logistically difficult because of the unpredictable weather on Kodiak.

An improved sampling design could reduce survey costs while yielding accurate and precise

parameter estimates.

CITATIONS

Caughley, G. 1970. Eruption of ungulate populations, with emphasis on Himalayan thar in New

Zealand. Ecology 51:53-72.

Hobbs, N. T. 1996. Modification of ecosystems by ungulates. Journal of Wildlife Management

60:695-713.

Lowell, R. E. 2008. Unit 1B mountain goat management report. Pages 17-35 in P. Harper, editor.

Mountain goat management report of survey and inventory activities 1 July 2005-30 June

2007. Alaska Department of Fish and Game, Juneau, Alaska.

McDonough, T. J. 2008. Units 7 and 15 goat management report. Pages 98-11 in P. Harper,

editor. Goat management report of survey and inventory activities 1 July 2005 - 30 June

2007. Alaska Department of Fish and Game. Project 12.0, Juneau, Alaska.

Porter, B. 2008. Unit 1A mountain goat management report. Pages 1-16 in P. Harper, editor.

Mountain goat management report of survey and inventory activities 1 July 2005 - 30

June 2007. Alaska Department of Fish and Game, Juneau, Alaska.

Rice, C. G., K. J. Jenkins, and W.-Y. Chang. 2009. A sightability model for mountain goats.

Journal of Wildlife Management 73:468-478.

Seber, G. A. F. 1992. A review of animal abundance II. International Statistical Review 60:129-

166.

Smith, R. B. 1986. Unit 8 mountain goat survey-inventory report. Pages 34-35 in B. Townsend,

editor. Annual report of survey inventory activities. Part VII. Mountain goat. Vol.

XVII. Alaska Department of Fish and Game, Juneau, Alaska.

Spear, D., and S. L. Chown. 2009. Non-indigenous ungulates as a threat to biodiversity. Journal

of Zoology 279:1-17.

Udevitz, M. S., B. S. Shults, L. G. Adams, and C. Kleckner. 2006. Evaluation of aerial survey

methods for Dall's sheep. Wildlife Society Bulletin 34:732-740.

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Figure 1. Track of survey planes during mountain goat aerial surveys, Kodiak Island, 2011.

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Figure 2. Mountain goat group locations (waypoints) recorded during aerial surveys, Kodiak Island, 2011. Group size is represented

by the size of the circle.

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Table 1. Summary of mountain goat survey results by hunt area, Kodiak Island, Alaska, 2011.

Hunt Area # Goats # Adults # Kids Kids: 100 Adults

471 123 103 20 19

472 85 85 0 0

473 115 97 18 19

474 259 219 40 18

476 94 87 7 8

478 205 163 42 26

479 121 97 24 25

480 1568 1277 263 21

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Figure 3. Number of mountain goats counted during years when surveys were considered

“island-wide” counts (in red) and logistic growth model (thin black line), Kodiak Island, Alaska,

1953-2011.

R² = 0.98

0

500

1000

1500

2000

2500

3000

3500

# G

oat

s

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Figure 4. Mountain goat survey results by Hunt Area, Kodiak Island, Alaska, 1975-2011. Survey effort varied by year, and not all

Hunt Areas were surveyed each year. Note that the y-axis scale differs between plots.

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Figure 5. Map depicting group sizes and the relative proportion of adults (red) and kids (yellow) counted in mountain goat hunt areas,

2011, Kodiak Island, Alaska.

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Table 2. Summary of mountain goat survey results from the past 10 years, Kodiak Island, Alaska. Data were collected by ADF&G

and KNWR biologists. Survey effort varied annually. Island-wide surveys were conducted in 2008 and 2011.

Year # Goats Kids: 100 Adults

2002 965 27

2003 781 23

2004 644 24

2005 1686 23

2006 577 22

2007 1674 20

2008 1975 23

2009 1028 26

2010 950 18

2011 2364 20