Showing posts with label natural history. Show all posts
Showing posts with label natural history. Show all posts

Friday, December 17, 2010

Crocodile Skinks of the South Pacific


Tribolonotus gracilis. JCM
Skinks come in a plethora of shapes and sizes, with about 1500 species they have invaded a huge variety of habitats and evolved a great diversity of life styles. They are found in almost all landscapes that support squamates and are perhaps the most successful lineage of living reptiles – if the measure is by the number of species. Among the most bizarre skinks are the South Pacific Crocodile Skinks of the genus Tribolonotus. Currently 8 species are recognized and they inhabit northern New Guinea and the Admiralty, Bismarck and Solomon Archipelagoes. They are semi-fossorial lizards, often found under vegetation and in the vicinity of water. At least two species are known to vocalize, and they demonstrate parental care. Hartdegen et al. (2001) described defensive vocalizations and parental care in captive specimens. They observed females curled around their egg and when eggs were gently handled by the observer the female exhibited defensive open-mouth lunges. When eggs were left uncovered by human observers they were reburied by the female. Hatchlings stayed near their mother (within 2 cm) and on occasion they were observed resting on the female's dorsum for two weeks after hatching. Their overall appearance is distinctive; they have unusually heavily keeled or spinose scales and two unique characters, abdominal glands and volar pores (pores on the plantar and palmer surfaces).

Recently, Austin et al. (2010) used molecular techniques and found evidence that Tribolonotus originated on either Greater Bougainville Island or in New Guinea, and subsequently dispersed to surrounding islands multiple times. Maximum body size ranged from 40 mm in T. blanchardi (and T. schmidti was a close second at 41 mm) to 125 mm in T. ponceleti. The authors did not find a phylogenetic explanation for differences in body size, and suggest that it evolved as the result of character displacement and ecological factors.

Exactly what the sister of Tribolonotus is remains a point of contention. They have been considered lygosomine skinks, allied with the genera Sphenomorphus, Mabuya, and Egernia by various authors. However,  Donnellan (1991) found Tribolonotus gracilis, has 32 chromosomes, a similar karyotype, to Egerina but there were differences that did not allowed a firm conclusion.

Literature
Austin, C. C., E. N. Rittmeyer, S. J. Richards and G. R. Zug. 2010. Phylogeny, historical biogeography and body size evolution in Pacific Island Crocodile skinks Tribolonotus (Squamata; Scincidae). Molecular Phylogenetics and Evolution, 57:227-236.

Donnellan, S. C. 1991. Chromosomes of Australian lygosomine skinks (Lacertilia: Scincidae).Genetica 83:207-222.

Hartdegen, R. W., M. J. Russell, B. Young, and R. D. Reams. 2001. Vocalization of the Crocodile Skink, Tribolonotus gracilis (De Rooy, 1909), and evidence of parental care. Current Herpetology 2001(2). On-line.

McCoy, M., 2006. Reptiles of the Solomon Islands. Pensoft Publishing, Sofia-Moscow.

Saturday, June 5, 2010

Burmese Python Distribution in China Re-examined

Dave and Tracy Barker have published an updated summary of the distribution of bivittatus in China. They examine the distribution by province and analyze the known records for each. The most eastern record occurs at Naping in Fujian Province. It has also been recently reported from The Kimmen Archipelago on Queymoy Island. They found no records of the species in Guangxi, but note it is widely reported in the literature to be present. One record of a specimen from Jiangxi based on the literature appears to be based upon a visual sighting and a shed skin. P. bivittatus appears to be present in extreme southern Yunnan (on the Vietnam border) as well as extreme western Yunnan, avoiding the Shan Plateau. The authors consider the presence of bivittatus in Sichuan Province problematic. Both specimens were associated with urban areas and could represent human introduction.

Barker, D. G. and T. M. Barker. 2020. The distribution of the Burmese Python, Python bivittatus, in China. Bulletin of the Chicago Herpetological Society 45:86-88.

Monday, April 12, 2010

Human Fascination With Large Snakes is Ancient

There is evidence that humans have been moving the large snakes around for at least two millennia. Strabo’s encyclopedic work Geography is a description of the ancient Greco-Roman world. In this 2000 year old text the author reports seeing a snake in Egypt that was 9 cubits long (about 13 feet or about 4 m) that had been brought from India. The same appears true for the African Python complex (Python sebae). Bodson (2004) described, what she considers, the first herpetological expedition to capture a large African Python organized under Ptolemy II (290 to 246 BC). The expedition captured a large specimen in the area known as the Island of Meroe, which is not really an island but the area between the White Nile, the Blue Nile and the Atbara River (14-16°N latitude). This area is within the known range of Python sebae. There are no firsthand accounts of the 3rd century BC effort and Bodson's account is based on information in a ms from the 1st century BC, at least 200 years after the event. Therefore it is not surprising that the size and abilities of the snake were exaggerated. Accounts from the turn of the 19th century suggest people in the Philippines were using Reticulated Pythons (Broghammerus reticulatus) to control rodents, keeping them in their houses and places of business. This may have lead Brown and Acala (1970) to concluded that the presence of reticulatus on virtually all Philippine islands were the result of human transport. It is therefore not surprising that 15 foot Burmese Python (P. bivittatus) was found in Riverside, California's Lake Evan over the week end (April 9) and an 11 ft python of an unstated species was found in Cornwell, England on April 11. Of course people keep giant snakes as pets or for commercial breeding projects today. Human fascination with snakes is ancient and undeniable.