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 . Marine Toads (Sapo) Sheep . House Sparrows Donkeys . Boa constrictors Rats (Black and Norway) . Blind snakes House Mice . Red-eared Slider Turtles Cats . Talapia Dogs . Rubber Vine
*Partial List 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?
Bubali N Paradera 150 m Oranjestad 100 m 50 m Plantage Prins n = 14 Hooiberg (166 m) Fontein n = 108 Quadirikiri n = 24 Butucu Jamanota (189 m) n = 13 Golf Club 1999 n = 11 2000 - 2003 San Nicolas n = 38 2 km Cero Colorado Largest Boas Can Be Over 2 Meters Most Are Less Than 2 Meters Boa populations – Stabilizing?
Boa constrictors Captured on Aruba
350 300+ 330 (Projected) 300 273 266 250 242 248 200 150 156 100 (June) 74 Number of Number Snakes 50 40 5 36 0 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 Year
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 Temperature on Aruba
28.8 Aruba: 28.6 28.6 28.6 28.6 28.5 28.4 28.5 28.3 28.3 Warmer 28.2 28.1 28.0 28.0
27.8 Average Annual
Temperature (C) and Wetter 27.6 27.4 1999 2000 2001 2002 2003 2004 2005 2006 2007 Weather Year
Precipitation on Aruba
1000.0 907.8 May have favored 836.6 800.0 780.6 611.0 population growth 600.0 555.2 501.6 508.8 400.0 of the 200.0 206.2 161.8 0.0 Total Annual Rainfall (mm) Boa Constrictor 1999 2000 2001 2002 2003 2004 2005 2006 2007 Year Diet and Reproduction 15 Baby Boas Prey
Lizards = 33.3 %
Mammals = 40.0 % A high proportion of the mammals and birds eaten by Boas are non-native, invasive Birds = 26.7% species. Aruba Island Rattlesnake Diet Lizards Mammals 42.4% 48.5% Comparison
Birds 9.1%
Dietary Overlap = Boa Constrictor
Lizards 82% 33.3% Mammals 40.0% Boas eat more birds Birds 26.7% Radiotracking Examines Behavior Movements of Radio-tracked Boas
Boa 18 Boa 21
(9 months) (4 months) 500 500 m
Small Activity Ranges and Repeated Return to Specific Sites Preferred Habitat of the Boa Habitat Relationship between Boas and Cascabels
Multivariate 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
(>99%) 100 90 80 (76%) C. unicolor 70 B. constrictor 60 50 40 30 (24%) 20 10 (<1%) Frequency of Observation (%) of Observation Frequency 0 On Surface In Trees 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
18 16 14 12 10 8 6 4
Number of Birds Numberof 2 0
9/15/2006 1/15/2007 2/15/20073/15/2007 4/15/2007 10/15/200611/15/200612/15/2006 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 ANTANERO B OA C ASCABEL (Leptodeira bakeri) (Boa constrictor) (Crotalus unicolor)
The slender Santanero or Aruban Cat-eyed Boas are Aruba’s largest snakes. The The small Cascabel or Aruba Island Snake is typically less than 50 cm long. This longest Boa found on the island was slightly Rattlesnake averages 70 cm in length. The snake is recognizable by the large scales on less than 3 m. Newborn Boas average 35 cm. body color is often uniform gray or light the top of its head and by its pattern of dark Boas are not venomous. The most distinctive brown. There may be a faint pattern of brown bands alternating with light brown feature of a Boa is its pattern of dark brown diamond shaped markings on the back. This bands. The belly is plain white or cream and tan blotches which become red toward pattern is most noticeable on younger colored without any markings. the tail. The belly in white or cream colored snakes. The most distinctive feature of this This snake is shy and not aggressive. with numerous black spots. snake is the rattle at the end of its tail which However, it has enlarged teeth at the back Boas are excellent climbers and may be makes a buzzing sound when the snake is of its mouth and mild venom which is not found in trees and cactus. Boas also hide in alarmed. dangerous to humans. However, the venom the leaves under bushes waiting to catch Cascabels are shy and not aggressive, but can paralyze small lizards and frogs. prey that pass. Boas catch their prey with their venom can be dangerous to humans. It Santaneros are most active at night when their teeth and then constrict it in their is best to leave this snake alone. Do not they search for food. During the day, they coils. The Boa’s diet consists of birds, attempt to catch or kill it. hide under rocks or leaves. They frequently lizards, rats, mice, and rabbits. Large Boas Cascabels hunt by waiting under bushes climb trees and cactus. Santaneros eat toads, have been known to eat small goats and and fruiting trees to catch passing lizards, frogs, insects, and lizards. chickens. When threatened, Boas will hiss mice, rats, small rabbits, and an occasional You may find Santaneros near dams loudly. bird. during periods of rainy weather or crossing Boas are a non-native species. The first This is often considered to be one of the roads at night. This snake is found island Boas were reported on the island in 1999. rarest rattlesnakes in the world. The range of wide. Since that time they have been found across the Cascabel is restricted to the rugged and the entire island in all types of habitats. 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?