Food availability induces geographic variation in reproductive timing of an aquatic oviparous snake ( Natrix maura (original) (raw)
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Revue d'Écologie (La Terre et La Vie)
Succès reproducteur individuel et taille de ponte dans une population de la couleuvre semi-aquatique Natrix tessellata en Italie centrale : les plus petits mâles et les plus grandes femelles sont-ils avantagés ? — Le succès de la formation des couples et de la reproduction de Natrix tessellata, serpent semi-aquatique, a été étudié dans le centre de l’Italie. Le succès des appariements a été établi en suivant par radiopistage 10 mâles et 12 femelles durant la période d’accouplement et en comptant combien chaque individu avait de partenaires sexuels en fonction de sa taille corporelle (longueur museauanus). Les femelles étaient significativement plus grandes que les mâles. Deux patrons opposés de succès individuel ont été mis en évidence dans la population : un succès d’appariement plus grand pour les plus petits mâles et pour les plus grandes femelles. De fait, chez les mâles, il y avait une relation significative entre la taille du mâle et le nombre de femelles avec lesquelles il s’...
Basic and Applied Herpetology, 2014
The energy gained by an organism is used for maintenance, growth and reproduction. In habitats with limited resources, these processes compete for available energy and may induce intraspecific variation in body condition, growth trajectories and reproductive output. We tested the hypothesis that populations exposed to higher food availability are able to grow faster, and attain larger body sizes in the viperine snake (Natrix maura). We estimated snake age by counting growth lines in the skull's ectopterygoid bone, and compared body size growth curves from three Iberian populations exposed to temporal variation of food resources availability. In the three localities, and in males and females, the growth curves followed a quadratic function that tended to an asymptotic value as growth slowed down. Growth curves showed slower growth rates and an early asymptote for males, in agreement with the reverse sexual dimorphism in body size of this species. We also detected interpopulational differences, with the Ebro Delta population exhibiting slower growth rates and smaller asymptotic body size in both sexes. This population inhabits rice fields with an artificial waterflow cycle, a condition that implies a shorter period of prey availability for snakes, compared to the other two populations, where prey is available for longer periods of time. Moreover, high proportion of snakes with tail breakage in this population indicated high predation pressure. These environmental conditions suggest that food availability and predation pressure may be concurrently acting to produce smaller N. maura at the Ebro Delta than at the other two populations.
Oikos, 2001
X. Bonnet, G. Naulleau, R. Shine and O. Lourdais Bonnet, X., Naulleau, G., Shine, R. and Lourdais, O. 2001. Short-term versus long-term effects of food intake on reproductive output in a viviparous snake, Vipera aspis. -Oikos 92: 297-308.
Journal of Animal Ecology, 2002
The ways that fluctuations in prey abundance and weather conditions can affect reproductive output in a 'capital breeding' ectotherm, the aspic viper (Vipera aspis) were examined. 2. Our longitudinal study confirms that female aspic vipers adjust reproductive investment by integrating allocations of energy from stores ('capital') and facultative feeding ('income'). Thus, long-term energy storage enabled females to reproduce successfully even in years when prey were scarce. 3. Not surprisingly, temporal changes in body reserves of female vipers preparing for reproduction depended upon current feeding rates. However, the mean environmental temperature during the active season also affected mass gain. 4. Allometric patterns suggest that reproductive output was limited by energy availability in 8 out of the 9 years of our study. In the other year, high prey availability in the preceding season meant that reproductive output was maximized within the constraints set by maternal body size (and thus, abdominal volume). 5. High summer temperatures increased basking opportunities of gravid vipers and thus accelerated gestation. However, maternal metabolic costs also increased in such situations, resulting in low postpartum body condition.
Frequency and effort of reproduction in female Vipera aspis from a southern population
Acta Oecologica, 1999
The frequency of reproduction of the asp viper (Vipera aspis, Viperidae) was studied in a population living along the coasts of central Italy. An annual reproductive cycle seemed to be the rule during the 5-year study period. Annual reproduction, high average mass of reproductive females, and large size of neonates, compared with other northern or continental populations, are presumably due to the particularly suitable climatic conditions of the area, as in most coastal habitats of the Mediterranean region. Such a scenario should influence the extent of the feeding period, which allows females, within a few months after parturition, to regain their previous body condition and reproduce again the following year.
Journal of Zoology, 2004
A study of individually marked smooth snakes Coronella austriaca was carried out in Wareham Forest, southern England between 1992 and 2001. On average, approximately one-third of potential breeding females reproduced each year and within this group, the proportion breeding was positively correlated with snout-vent length (SVL). Successful breeders had a higher than average body condition at the start of the breeding year compared with unsuccessful breeders. The density of gravid females was positively correlated with prey density in the breeding year but not in the year preceding it. No significant relationships were found between the density of non-breeding females and prey density in either the breeding year or the preceding year. Although most breeding females did not produce young in consecutive years, a small proportion did. There was a weak positive relationship between clutch size and female SVL. This study suggests that the potential for female smooth snakes to breed is provided by stored energy reserves but that this potential is regulated by prey availability in the breeding year.
Long-term population dynamics in a Mediterranean aquatic snake
Ecological Research
A review of several long-term studies has recently suggested that snakes might be declining in large parts of the world. Additional data from other long-term studies are therefore urgently needed in order to assess the generalities of such suggested declines. Based on a 20-year study, we analyzed demographic data on adult dice snakes (Natrix tessellata) studied in central Italy between 1985 and 2004. Both male and female dice snakes were relatively long-lived, with no significant differences in longevity between the sexes. Individual males and females were observed over a maximum of 10 and 14 years, respectively. However, the among-year recapture rates between the year the snakes were initially captured and the subsequent year (i.e., year 1 to year 2) was significantly lower (45%) than the among-year recapture rates during subsequent years (74%; i.e., year 2 to year 3), suggesting that a large proportion of the snakes at first capture were in fact not resident within our study area, and hence many snakes were migrating in and out of our 2-km stream study site, with no inter-sexual difference in dispersal rates. Sex ratio was virtually equal if we consider the study period as a whole. Significant annual fluctuations were, however, observed through the study. In 1985–1990, 1993–1995, 1998 and 1999 the sex ratio was male-biased, whereas in 2000–2004 female-biased. In terms of both survival and recapture probabilities, model selection showed that Akaike’s information criterion favored the model incorporating body size, with the model incorporating year having an intermediate likelihood, and the model with sex included being the most disfavored. Total population number estimates suggest an average 86 adult individuals along the 2 km of stream with only minor annual variations. However, a significant decrease in the number of males occurred during the last 6 years of our study. Thus, further monitoring of this population is warranted in light of the decline of snake populations reported recently.
American Midland Naturalist, 2000
We studied the ecology of the checkered garter snake, Thamnophis marcianus, in a desert grassland in southeastern Arizona. The adult sex ratio was 0.67 M : F and varied significantly among seasons. As with other species of Thamnophis, adult females were significantly larger than males in SVL and body mass, and females also had longer jaws. Activity occurred both during the day and nighttime, but was confined to aquatic areas or their immediate vicinity. Mating occurred in late March and females gave birth to a single brood of an average of 15 offspring in late May and early June. The timing of birth in this population was among the earliest on record for any live-bearing snake in North America and was much earlier than for other checkered garter snake populations. In comparison with populations of T. marcianus from northern and southern Texas, females from Arizona had larger maternal body sizes and their offspring were larger as well; conversely, we found no significant differences in brood size among localities once maternal body size was taken into account. The implications of early timing of birth and geographic variation in reproductive traits are discussed.