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?