Ecological patterns of relative clutch mass in snakes

Abstract

Data on the relative clutch mass of snakes are summarized for over 100 populations. RCM was significantly lower in live bearing versus egg laying forms. We suggest that the longer reproductive season of viviparous snakes results in higher overall mortality compared to oviparous species; by reducing RCM, viviparous snakes may reduce this risk of mortality. Unlike lizards, no differences in RCM were found between categories of either escape behavior or foraging mode, possibly because detailed information on these behaviors are lacking for most snakes. In four populations examined, RCM did not vary among years. When compared to lizards, snakes demonstrate significantly higher RCM, perhaps owing to a more energetically efficient means of locomotion. Our data support the contention that RCM should be considered a separate and distinctive life-history characteristic of reptiles.

Relative Clutch Mass and Body Shape in Lizards and Snakes: Is Reproductive Investment Constrained or Optimized?

“…In some comparisons, differences in body shape can account for some but not all ofthe differences in RCM (e.g., Sceloporus versus Cnemidophorus: 20% difference in ratios ofabdominal volume to body mass, versus 73% difference in RCMs: Table I), so that taking body shape into account decreases the magnitude of the difference in RCMs, but does not eliminate it. In contrast, the higher RCMs of snakes than of lizards overall (Seigel and Fitch, 1984;Dunham et al, 1988; Table I) may be entirely attributable to differences in body shape. The ratio of abdominal volume to body mass is almost twice as high in snakes as in lizards (Table I), and hence there is little difference between snakes and lizards in clutch mass relative to abdominal volume.…”

“…Evolutionary determinants of reproductive rates in squamate reptiles have attracted considerable scientific attention, especially in terms ofthe relative clutch mass (RCM) (ratio of clutch mass to maternal mass: e.g., Vitt and Congdon, 1978;Vitt, 1981;Vitt and Price, 1982;Seigel and Fitch, 1984;Shine, 1988;Dunham et aI., 1988;Anderson and Karasov, 1988;Shine and Schwarzkopf, 1992). Several broad patterns in RCM variation among squamates have been identified.…”

“…Several broad patterns in RCM variation among squamates have been identified. For example, "wide-foraging" cnemidophorine lizards tend to have lower RCMs than do "ambush predators" of the genus Sceloporus (Vitt and Congdon, 1978), RCMs are low in anoline and gekkonid lizards with fixed clutch sizes (Andrews and Rand, 1974;Vitt and Congdon, 1978), RCMs are lower in lizards than in snakes (Seigel and Fitch, 1984), and aquatic snakes have lower RCMs than do terrestrial species (Shine, 1988). Nonetheless, the relative importance oftradeoffs and constraints in producing such patterns remains problematical.…”

Biometry and pholidosis of Thamnophis scaliger: an atypical example of sexual dimorphism in a natricine snake

“…Within T. scaliger, females achieve greater body length than males, a general characteristic for this and other natricine colubrid snakes (FITCH, 1981). Female snakes that make a significant investment in reproduction tend to attain larger body size than males (SHINE, 1993;BONNET et al, 2000), and T. scaliger is not an exception, as postpartum relative clutch mass is rather high (55% on average, authors' unpublished data) compared to values from other ovoviviparous species (SEIGEL & FITCH, 1984).…”

Variações em caracteres morfológicos e ecológicos em populações de Bothrops jararaca (Serpentes: Viperidae) no estado de São Paulo

“…Para as serpentes, tal relação já havia sido documentada para B. jararaca (JANEIRO-CINQUINI et al, 1990;SAZIMA, 1992;JANEIRO-CINQUINI, 2004b; ALMEIDA-SANTOS, 2005) e é amplamente difundida em táxons de diversos gêneros (e.g. FITCH, 1981;SEIGEL & FITCH, 1984;1985;FITCH, 1985;SHINE, 1986;PARKER & PLUMMER, 1987;VITT, 1992;MADSEN & SHINE, 1994;MARQUES, 1996a;b;PIZZATTO & MARQUES, 2002), incluindo o gênero Bothrops NOGUEIRA et al, 2003;HARTMANN et al, 2004). Isso ocorre simplesmente devido às fêmeas maiores disporem de maior espaço físico para acomodar ovos ou filhotes em desenvolvimento RIVAS & BURGHARDT, 2001).…”