Sexual Dimorphism and Niche Divergence: Feeding Habits of the Arafura Filesnake

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. Sex-based differences in diets are widespread among animals, but may often reflect sex differences in body size or in the times and places that feeding occurs, rather than sex-specific prey-selection behaviour. We examined these hypotheses with detailed information on the types and sizes of fishes consumed by filesnakes, Acrochordus arafurae McDowell, 1979, based on a 4-year field study in the Wet-Dry tropics of northern Australia. 2. These aquatic snakes show extreme sexual dimorphism in body length, body shape, relative head size, head shape, foraging habitat and diet. The composition of the diet varied seasonally and with the size as well as the gender of the snakes. Both sexes ate more frequently during the Wet season, apparently because of higher prey availability at this time. 3. Both sexes showed significant selectivity of prey species, but differed profoundly in food habits. Female filesnakes generally consumed only a single large prey item at a time, whereas the stomachs of males typically contained many small prey items. 4. Males were relatively unselective foragers, with little evidence of ontogenetic shifts in prey size or prey type. In contrast, large females ate larger prey items, and showed an ontogenetic shift from a generalized (male-like) diet to 'sleepy cod' (eleotrids) and finally to plotosid catfish. 5. When comparison was restricted to snakes of the same head length, males and females differed significantly in dietary composition and in prey sizes, but not in feeding frequencies or the relative numbers of snakes containing single versus multiple prey items.

Polar Bear Diets and Arctic Marine Food Webs: Insights From Fatty Acid Analysis

“…Intraspecific differences in dietary diversity have been observed in a variety of predators including marine mammals (Beck et al 2007), mustelids (Birks and Dunstone 1985), and reptiles (Houston and Shine 1993). Differences in dietary-niche breadth may be a consequence of larger animals being either (1) less selective, perhaps in order to meet increased energy requirements (e.g., Clutton-Brock et al 1987), or (2) more selective, and able to focus predation on larger, higher-quality prey (Houston and Shine 1993).…”

“…Differences in dietary-niche breadth may be a consequence of larger animals being either (1) less selective, perhaps in order to meet increased energy requirements (e.g., Clutton-Brock et al 1987), or (2) more selective, and able to focus predation on larger, higher-quality prey (Houston and Shine 1993). Among polar bears, large adult males had the greatest dietaryniche breadth likely because of their ability to capture large prey as well as take kills away from smaller bears.…”

Reproductive strategies in snakes

“…This emphasis has many implications. Female snakes, for example, often grow larger than conspecific males (thus increasing fecundity; Shine 1994), have larger heads relative to body length (thus eating larger prey; Houston & Shine 1993), are more heavy-bodied (reflecting energy storage; Scott et al 1995;Madsen & Shine 2002), and coordinate their reproductive decisions with temporal fluctuations in energy availability (Madsen & Shine 2000b;Bonnet et al 2001). Because many macrostomate snakes rely on infrequent ingestion of large prey items (Greene 1983), food intake may be low relative to maternal body size.…”

Morphological variation of Philodryas patagoniensis (Girard, 1858) (Serpentes, Dipsadidae) from Brazil, based on the study of pholidosis, coloration and morphometric features

“…Although sexual dimorphism in HL is related to dietary differences as suggested by Pough & Groves (1983), Forsman (1991), Shine (1986Shine ( , 1991, Houston and Shine (1993), Forsman (1996), King (2002), Shetty & Shine (2002), Nogueira et al (2003), Aubret et al (2004), Vincent et al (2004), and López et al (2013). The differences found in HL between males and females of P. patagoniensis are not related to diet (Hartmann & Marques 2005, López & Giraudo 2008.…”