Ophidiomycosis surveillance of snakes in Georgia, USA reveals new host species and taxonomic associations with disease

Ophidiomycosis (snake fungal disease) is caused by the fungus Ophidiomyces ophiodiicola and threatens snake health worldwide. It has been documented throughout the eastern United States and severe cases have recently been reported in Georgia, USA. To evaluate disease distribution and prevalence in this state, 786 free-ranging snakes were examined for skin lesions consistent with ophidiomycosis and swabbed to detect O. ophiodiicola DNA using qPCR. Sampled snakes represented 34 species and 4 families; 27.5% had skin lesions, 13.3% were positive for O. ophiodiicola DNA, and 77.8% of the qPCR positive individuals had skin lesions. This is the first report of O. ophiodiicola in five of the 22 species that were qPCR positive. Multinomial logistic regression modeling indicated that Drymarchon couperi had a higher relative risk of apparent ophidiomycosis (lesions present and qPCR positive), and the best models predicting qPCR result and ophidiomycosis category included individual factors and excluded temporal and spatial factors. Phylogeny-based bipartite network analysis showed that Nerodia erythrogaster, Nerodia taxispilota, and D. couperi had the highest prevalence of apparent ophidiomycosis; this category was more prevalent in the subfamily Colubrinae and less prevalent in Natricinae. These results provide important information about ophidiomycosis epidemiology, which has implications for snake conservation.

The relationship of head morphology and diet among three sympatric watersnake species

Investigating dietary resource utilization and head morphology of gape-limited predators can provide a basis for understanding interspecific competition and species coexistence. For sympatric species, convergence of head morphology can indicate similar prey or foraging strategies while divergence can suggest competition, resource partitioning or expansion into new habitats. Sexual dimorphism can further complicate the head morphology-diet relationship by potentially reducing intraspecific competition. To understand the relationship between head morphology and diet, we studied three sympatric species, the plain-bellied (Nerodia erythrogaster), diamondback (N. rhombifer), and northern (N. sipedon) watersnakes in western Kentucky. All three species inhabit similar wetlands and feed on amphibians and fishes. The anurophagous plain-bellied watersnakes had longer, narrower heads that likely allow snakes to capture anuran metamorphs and froglets while facilitating movement through dense vegetation. The piscivorous diamondback watersnake had a wider head, which would enhance contact with prey in this open-mouth forager, and smaller interocular distance, resulting in dorsally placed eyes that facilitate seeing fish prey from below. The mostly piscivorous northern watersnake had an intermediate, generalized head shape, which may reflect the typically wide diet range of this species. Head shape did not differ between snake sexes but diamondback and northern females had larger heads than males and fed more frequently on fishes. The relationship between head morphology and diet highlights potential interspecific and intersexual competition and aids in the understanding of species coexistence patterns.

Primer registro de Nerodia erythrogaster bogerti (Conant, 1953) (Serpentes: Colubridae) para el estado de Chihuahua, México

We present the first record of Nerodia erythrogaster bogerti from Chihuahua, the new record extending its known range ca. 480 km (air distance) N from the closest locality, in the Nazas River Basin.

Primer registro de Nerodia erythrogaster bogerti (Conant, 1953) (Serpentes: Colubridae) para el estado de Chihuahua, México

We present the first record of Nerodia erythrogaster bogerti from Chihuahua, the new record extending its known range ca. 480 km (air distance) N from the closest locality, in the Nazas River Basin.

Effects of flood suppression on natricine snake diet and prey overlap

Organisms may become adapted to disturbances when these disturbances occur periodically and at intermediate intensity. To investigate the effects of flood suppression, this study compared diet and competition of semi-aquatic snakes during flood (2000–2001) and no flood (2003–2005) years. Three natricine species, Nerodia erythrogaster (Forster in Bossu, 1771), Nerodia fasciata (L., 1766), and Thamnophis proximus (Say in James, 1823), were palpated for prey items in an east Texas floodplain under both conditions. Prey items were classified as crayfish, salamanders, anurans, or fish. Simpson’s diversity index of prey, frequency of consumed prey type, and prey importance values were compared between flood and no flood years. Pianka’s index of niche overlap was used to compare changes in diet overlap between species in the years with floods and those without. In the absence of floods, the number of prey types consumed by N. erythrogaster and T. proximus decreased. The frequency of prey types consumed during flood years was significantly different from the period of flood suppression for all three species. The order of prey importance also changed in the absence of floods for all three snake species. Without floods, diet overlap decreased between N. erythrogaster and the other two species; however, overlap between N. fasciata and T. proximus doubled.