A night out on Tobago

Walking in the oldest protected forest in the Western Hemisphere at night you expect to see frogs, lizards, and snakes as well as interesting arthropods and the occasional mammal, on Tobago this might be an agouti or an armadillo. What you don't expect are feral dogs. Eight of us were surveying the herpetofauna on Thursday night only to find we had been joined by two dogs. They were friendly enough, and accompanied us along the trail  from the beginning to the end. It was a interesting walk with several of the endemic Trinidad and Tobago frogs calling as well as an Oxybelis aeneus sleeping on a branch above the trail and an Imantodes cenchoa stalking a Pristimantis urichi. We came off the trail at a point that required a hike back to the car. Here we encountered a third dog, it was lying curled in the grass, a necrotic ear, swollen jaw, and visible ribs and its behavior suggested it was dying. Lacking a way to kill it quickly we returned to the cars.

One of our canine companions. 

While we were all sympathetic to the dogs they do not belong there, they cause damage to wildlife populations, as well as being a potential human health problem.

The winding road between Charllottville and Speyside on Tobago can be treacherous for both humans and animals. There are a large number of blind curves and when combined with reckless driving (a very common problem on the island) the results can be lethal. While returning from field work a car with its flashers on had pulled over to the side of the road and the people were standing in the road at a relatively wide spot. We slowed down, and then stopped when we saw the 2.2 m boa in the road. Some of us directed traffic around the snake while others took photographs; all the while being warned by an intoxicated on-looker that the snake would bite us if we got too close. The gravid female was quite tolerant of the flashes and people moving around her.

The 2.2 m boa constrictor.

This was the fifth Boa constrictor we had seen during the week. All of the others were road kill, except one that had been dispatched with a machete. After taking a few photos, we dragged the snake off the road.

Boa constrictors are the largest predators on the island with the exception of humans and could be used to help control feral dogs and cats if people would only leave them alone. An education program for residents that emphasizes not killing snakes and not releasing or dumping household pets, as well as keeping them locked up at night, could go along way toward protecting snakes and the forest as well as solving the feral pet problem.

Aquatic post-escape behavior of the green iguana on Tobago

Green iguanas are well known for diving into streams from arboreal basking sites, but their behavior under water after the escape has to my knowledge not been reported, other than they swim away. While hiking in the Hillsborough River on Tobago on the morning of  7 June a one meter (total length) green iguana (Iguana iguana) dove into the river as we approached. After looking around the area for about 10 minutes I returned to the area where the iguana had been seen. Walking the shoreline the green and black bands of an iguana tail were visible underwater and upon closer inspection the lizard was lying on the bottom of the stream (about 40 cm deep) slightly under the bank and some floating roots. The lizard was less than 15 meters from its original point of entry into the stream. The lizard did not surface or move during  10 minutes  of observation. Several photographs were taken, and then I waded into the water and approached the lizard, for more photographs. During this time the iguana flicked its head several times in response to a crayfish that was touching its nose, but it did not respond to my presence even when I was less than half a meter from it, and bent directly over the lizard for more photographs. When two students approached on land, a leaf had drifted over the lizard's head and so they could also view and photography the lizard I reached into the water within a few centimeters of the head and removed the leaf. Again the lizard did not respond to my presence. Only when one of the students slipped in the stream did the lizard move, and it slowly swam away. Like many cryptically colored species, the green iguana relies on its camouflage to avoid predation underwater, but not in arboreal or terrestrial situations.

The submerged green iguana relying on its coloration to avoid detection. JCM

Close-up of the submerged lizard's crown. JCM

Frogs, ecotourism, and litter

After a day of monsoonal rains the hylid fog Trachycephalus typhonius move to a breeding pond, males start to call, and soon the noise becomes overpowering. Just off the Northside Road in Tobago one of the most spectacular auditory displays in the amphibian world, and in all of nature, could be seen and heard. On June 3rd, we found a chorus than consisted of hundreds of individuals. Males pushed and chased other males away when they came too close. Females were picking males to amplex with, probably based on the qualities of the male's call, but the position of the male within the chorus. An important choice that will influence the success of her genes in the next generation. Satellite males were frequently standing by pairs in amplexus, and males were frequently challenging each other. Other herps nearby included the rattle-voice treefrog, Hypsiboas crepitans and the tungara frog, Eupemphix pustulosus, as well as the slug-eating snake, Sibon nebulata, and the cat-eyed snake, Leptodiera annulata.

Male Trchycephalus chasing way a competitor, note blue fabric at bottom left. JCM

The Trachycephalus chorus is one of those spectacular events that everyone appreciates when they see it. However, this particular chorus was marred by the fact that the breeding pond was full of bottles, cans, plastic containers and styrofoam trays. Trinidad and Tobago could develop an ecotourism industry around the herpetofauana as they have for birds - chorusing Trachycephalus would be a high interest event that would draw people from all over the world. People who would be staying in hotels, eating in restaurants, and paying tour guides. But, the trash problem needs to be solved first.

Calling male Trachycephalus amid debri. JCM