Successful lizard eggs in a human-disturbed habitat

Abstract

As humans extend their influence to an increasingly large portion of the globe, it becomes of both theoretical and practical interest to understand the consequences of our activities on wildlife populations. Norops polylepis is a small anoline lizard native to rainforest of southern Costa Rica. It is also found and known to lay eggs in cattle pastures immediately adjacent to forest. I predicted that N. polylepis eggs would fare poorly in pastures because of the important abiotic and biotic differences with their native forest habitat. I obtained eggs from captive females and estimated an egg's probability of hatching, daily survival rate, and incubation time at various distances along a forest-to-pasture gradient. Contrary to expectation, egg survival rates were higher in pastures than in forest areas. Furthermore, egg incubation times were significantly shorter in pastures than in their native forest. As a result, eggs were at least as likely to hatch in pastures as in forested areas. Thus, pastures may represent a benign or even beneficial habitat for the eggs of some reptile species. High survival of eggs will facilitate range expansion into human-altered habitats such as pastures, but does not guarantee it. Indeed, pastures could represent an ecological trap and a population sink if adults are drawn there (e.g., in search of favorable ovipositioning sites) yet suffer higher mortality than in forests.

The Occurence of Ecological Traps in Bird Populations: Is our Knowledge Sufficient? A Review

“…and/or indirect cues (e.g. the number of individuals of the same species or absence of a predator; Andrén 1990; Kokko and Sutherland 2001;Schlaepfer et al 2002;Schlaepfer 2003;Roos and Pärt 2004;Eggers et al 2005). The more complete information an individual has about a given biotope, the better is its judgement (Battin 2004;Kokko and Sutherland 2001).…”

Effects of off-road vehicles on reproductive success of pine snakes (Pituophus melanoleucus) in the New Jersey pinelands

“…Some attention has focused on reptiles, particularly on disturbance to nesting turtles and lizards (Schlaepfer 2003;Jessop and Hamann 2004;Moore and Seigel 2006), effects on basking or foraging reptiles (Burger 2001;Parent and Weatherhead 2000;Goldingay and Newell 2000), effects of roads (Garber and Burger 1995;Gibbs and Shriver 2002), effects of livestock on nesting reptiles (Homyack and Giuliano 2002;Semlitsch and Bodie 2003), and the effect of forest management on reptile assemblages (Brown 2001;Russell et al 2002). The lack of studies with snakes is largely because of their solitary or secretive nature and the difficulty of observation.…”

Enigmatic Faunal Declines at La Selva, Costa Rica: Patterns and Processes in a Collapsing Neotropical Herpetofauna

“…Perhaps even more important than stable temperatures is increased humidity found in deep leaf-litter. Amphibians are particularly sensitive to drought, and experimental studies have indicated that eggs of lizards of the genus Norops also experience high mortality associated with desiccation (Schlaepfer 2003, Socci et al 2005. While I originally sought to measure humidity in association with temperature, I experienced very high fail rate for humidity dataloggers within weeks of deployment.…”

“…Leaf litter provides shelter and refuge from predation (Cooper et al 2008a(Cooper et al , b, 2009). Finally, leaf litter creates a moist microhabitat on the forest floor, upon which amphibians depend to prevent desiccation, and upon which both lizards and terrestrially-breeding amphibians are critically dependent to prevent desiccation of vulnerable egg stages (Schlaepfer 2003, Socci et al 2005). …”