boa constrictor on aruba.wildaruba.org/documents/boaconstrictor-wildaruba.pdfthe ecology and...
TRANSCRIPT
The Ecology and Management of the Invasive
Boa constrictor on Aruba.
Howard K. Reinert1, William I. Lutterschmidt2,
Lauretta M. Bushar3, and R. Andrew Odum4
1Department of Biology, The College of New Jersey, Ewing, NJ 2Department of Biological Sciences, Sam Houston State University, Huntsville, TX
3Department of Biology, Arcadia University, Glenside, PA 4Department of Herpetology, Toledo Zoological Society, Toledo, OH
Non-native Species
All introduced, non-native species that become
established alter the natural community of plants
and animals in some way.
Their impact can range from minor to
devastating.
The extent of the impact depends upon both the
ecology of the invading species and the structure
of the existing, natural community.
Non-native Species on Aruba*
They are everywhere!
Goats
Sheep
Donkeys
Rats (Black and Norway)
House Mice
Cats
Dogs
*Partial List
Marine Toads (Sapo)
House Sparrows
Boa constrictors
Blind snakes
Red-eared Slider Turtles
Talapia
Rubber Vine
Even Aruba Aloe is Not Native
Major Concern
The impact of Boa Constrictors on the Aruba
Island Rattlesnake (Cascabel)
The Aruba Island Rattlesnake is special
The Boa Project on Aruba
Purpose:
Determine distribution
Learn about behavior and habitat preference
Learn about reproduction
Learn about diet
Assess potential impact
Examine possible control methods
Where Are Boas on Aruba?
San Nicolas n = 38
Oranjestad
Paradera
150 m 100 m 50 m
Jamanota (189 m)
Cero Colorado
N
2 km
Hooiberg (166 m) Fontein n = 108
2000 - 2003
1999 Golf Club
n = 11
Butucu n = 13
Quadirikiri n = 24
Bubali
Plantage Prins n = 14
Largest Boas Can Be Over 2 Meters
Most Are Less Than 2 Meters
Boa populations – Stabilizing?Boa constrictors Captured on Aruba
74
242
330
266248
273
5
40
36
156
0
50
100
150
200
250
300
350
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
Year
Nu
mb
er
of
Sn
akes
(June)
300+(Projected)
1999 to June of 2008: 1,670 Boas Removed
High Density Boa Populations in
Preferred Habitat
Primary
Study Area
Density =
11 boas/ha
Bag of 12 Boas Captured in 3 hours on a 10 ha Study Area
Aruba:
Warmer
and Wetter
Weather
Precipitation on Aruba
836.6
555.2
206.2
508.8
907.8
780.6
501.6611.0
161.8
0.0
200.0
400.0
600.0
800.0
1000.0
1999 2000 2001 2002 2003 2004 2005 2006 2007
Year
To
tal
An
nu
al
Ra
infa
ll (
mm
)Temperature on Aruba
28.3
28.1
28.5
28.0
28.6
28.328.5
28.6 28.6
27.4
27.6
27.8
28.0
28.2
28.4
28.6
28.8
1999 2000 2001 2002 2003 2004 2005 2006 2007
Year
Av
era
ge
An
nu
al
Te
mp
era
ture
(C
)
May have favored
population growth
of the
Boa Constrictor
Diet and Reproduction
15 Baby Boas
Prey
Lizards = 33.3 %
Mammals = 40.0 %
Birds = 26.7%
A high proportion of
the mammals and
birds eaten by Boas are
non-native, invasive
species.
Diet
Comparison
Aruba Island Rattlesnake
Mammals
48.5%
Birds
9.1%
Lizards
42.4%
Boa Constrictor
Mammals
40.0%
Birds
26.7%
Lizards
33.3%
Dietary Overlap =
82%
Boas eat more birds
Radiotracking Examines Behavior
Movements of Radio-tracked Boas
500 m
Boa 21
(4 months)
Boa 18
(9 months)
Small Activity Ranges and Repeated Return to Specific Sites
Preferred Habitat of the Boa
Habitat Relationship between Boas
and CascabelsMultivariate Habitat Overlap =
26%
Non-overlap exceeds what is theoretically necessary for coexistence.
Feeding on the Ground and in Trees
Boa Hunting In Fruiting Tree
Waiting for Lizards
Comparison of Site Use
Cascabel and Boa Locations
0
10
20
30
40
50
60
70
80
90
100
On Surface In Trees
Fre
qu
en
cy o
f O
bserv
ati
on
(%
)
C. unicolor
B. constrictor
(>99%)
(76%)
(24%)
(<1%)
Boas Spend Only 24% of Their Time
in Trees
Boas Spend Most of Their Time on
the Ground – Can You See Him?
Still Hard to See?
Trapping Experiments
Traps Placed With Boas
Boa Trapping Results
Bait Number of Trap-nights Number of Boas Captured
Pigeon 27 3
Rat 9 0
House Mouse 9 0
Female Boa 7 0
Lizard 6 0
Female Boa Shed Skin 5 0
Chicken 3 0
Chicken Extract (soup) 3 0
Total 69 3
Boas/trap-night 0.043
Trap Success 4.3%
Trapping Was Not Very Effective
Can Aruban Wildlife Survive the Boa?
Boas and Other Snakes Do Coexist
with Wildlife on Caribbean Islands
Isla Margarita – Boa Constrictor, Neotropical
Rattlesnake, Hog-nosed Viper
St. Lucia – Boa constrictor, St. Lucia Serpent
Dominica – Boa Constrictor
Paraguana – Boa Constrictor, Neotropical
Rattlesnake, Coral Snake
Aruba – Boa Constrictor, Cascabel?
Encouraging Findings
Cascabel populations appear stable for the
moment.
Habitats and behavior may differ enough to
allow coexistence.
Diets overlap considerably – but lizard
densities remain high in all habitats.
Situation should continue to be monitored.
Bird Frequencies Fluctuate –
No Clear Trend
Frequency of Birds Observed
on Boa Study Area
02468
1012141618
9/15
/200
6
10/1
5/20
06
11/1
5/20
06
12/1
5/20
06
1/15
/200
7
2/15
/200
7
3/15
/200
7
4/15
/200
7
Nu
mb
er
of
Bir
ds
Recommendations
Continue Current Boa Monitoring Program: (Reporting/Response/Removal/Recording)
Reporting by citizens
Response by trained personnel
Removal by trained personnel
Recording of data following euthanasia and examination.
A trained dog could be used to locate reported
or suspected Boas around residences.
Education
S A N T A N E R O (Leptodeira bakeri)
The slender Santanero or Aruban Cat-eyed Snake is typically less than 50 cm long. This snake is recognizable by the large scales on the top of its head and by its pattern of dark brown bands alternating with light brown bands. The belly is plain white or cream colored without any markings. This snake is shy and not aggressive. However, it has enlarged teeth at the back of its mouth and mild venom which is not dangerous to humans. However, the venom can paralyze small lizards and frogs. Santaneros are most active at night when they search for food. During the day, they hide under rocks or leaves. They frequently climb trees and cactus. Santaneros eat toads, frogs, insects, and lizards. You may find Santaneros near dams during periods of rainy weather or crossing roads at night. This snake is found island wide.
B O A
(Boa constrictor) Boas are Aruba’s largest snakes. The longest Boa found on the island was slightly less than 3 m. Newborn Boas average 35 cm. Boas are not venomous. The most distinctive feature of a Boa is its pattern of dark brown and tan blotches which become red toward the tail. The belly in white or cream colored with numerous black spots. Boas are excellent climbers and may be found in trees and cactus. Boas also hide in the leaves under bushes waiting to catch prey that pass. Boas catch their prey with their teeth and then constrict it in their coils. The Boa’s diet consists of birds, lizards, rats, mice, and rabbits. Large Boas have been known to eat small goats and chickens. When threatened, Boas will hiss loudly. Boas are a non-native species. The first Boas were reported on the island in 1999. Since that time they have been found across the entire island in all types of habitats.
C A S C A B E L
(Crotalus unicolor) The small Cascabel or Aruba Island Rattlesnake averages 70 cm in length. The body color is often uniform gray or light brown. There may be a faint pattern of diamond shaped markings on the back. This pattern is most noticeable on younger snakes. The most distinctive feature of this snake is the rattle at the end of its tail which makes a buzzing sound when the snake is alarmed. Cascabels are shy and not aggressive, but their venom can be dangerous to humans. It is best to leave this snake alone. Do not attempt to catch or kill it. Cascabels hunt by waiting under bushes and fruiting trees to catch passing lizards, mice, rats, small rabbits, and an occasional bird. This is often considered to be one of the rarest rattlesnakes in the world. The range of the Cascabel is restricted to the rugged and mountainous areas of the island mostly within Arikok National Park.
Monitor Wildlife Populations
Establish Monitoring Programs
Determine Trends
Watch for Changes
Lots of People Working Together
The Boa Research Project
It takes a joint effort to protect Aruba’s ecosystem:
Arikok National Park Foundation
Department of Agriculture, Husbandry and Fisheries
Department of Veterinary Services
The College of New Jersey
Toledo Zoological Society
Albo Aruba
Valero
Meta Corp
AHATA La Cabana
Renaissance
Talk of the Town
Amsterdam Manor
Holiday Inn
Playa Linda
Thank you.
Questions?