Physiological and Ecological Consequences of Sleeping‐Site Selection by the Galapagos Land Iguana (Conolophus Pallidus)

Abstract

Field observations and biophysical models were combined to analyze sleeping—site selection by Galapagos land iguanas (Conolophus pallidus). Iguanas slept in different kinds of sleeping sites during different seasons. In the coolest season (garua), adults land iguanas were found in sleeping sites that were warmer than the coolest sites a available. This may be because the garua season (cool, overcast, and foggy) is a time when environmental conditions mitigate against rapid warm—up in the mornings, so lizards may regulate nighttime body temperatures so that it is easier to warm up to preferred daytime body temperatures. In the warmest season, adult iguanas were found in the coolest sleeping sites available. This observation is consistent with hypotheses of voluntary hypothermia, which can be advantageous in energy conservation and in avoiding detrimental effects associated with maintenance of constant body temperatures throughout the day and night. Juvenile iguanas were found sleeping in rock crevices regardless of the ambient thermal environments. Such sites are likely to be important as refugia for this life stage, which, unlike the adult stage, is vulnerable to predation. We conclude that selection of sleeping sites is a process that may help in avoidance of predation, optimization of body temperature at the end of the sleeping period, and reduction of metabolic costs during sleeping. The importance of some of these factors may change with the thermal milieu (e.g., season).

Thermal plasticity in young snakes: how will climate change affect the thermoregulatory tactics of ectotherms?

“…We have no data on the mechanisms generating that growth-rate differential but suspect that it relates either to metabolic costs of frequent movement to fine-tune thermoregulatory behaviour to exploit all ambient opportunities; or a thermal difference among treatments that we did not detect because we measured body temperatures only on unfed snakes. Many snakes select higher temperatures post-feeding to accelerate digestion and perhaps increase its efficiency (Regal, 1966;Harwood, 1979;Naulleau, 1983;Christian et al, 1984;Sievert and Andreadis, 1999;Blouin-Demers and Weatherhead, 2001;Tattersall et al, 2004). If our hot-treatment snakes exploited the availability of high temperatures in this way (and we have no evidence that they did), it might explain the higher growth rates of these animals (i.e.…”

The behavioral physiology of labroid fishes

“…This "voluntary hypothermia" is thought to reduce energetic costs and is maximized by the selection of optimal sleeping sites in the land iguana Conolophus pallidus (Christian and Tracy, 1984 varies from species to species, but is generally lower in birds than in mammals (AyalaGuerrero, 1989). In mammals, the time spent in quiet sleep was negatively correlated with body size and basal metabolic rate (Elgar et al, 1988).…”

Watch out where you sleep: Nocturnal sleeping behaviour of Bay Island lizards

“…51 Sleep, a highly prevalent behavioural state across the animal kingdom (Siegel 2008), has been 52 hypothesised to serve many roles, including energy conservation (Christian et al 1984), neural 53 restoration (Siegel 2003) and predator avoidance (Meddis 1975;Lima et al 2005). The long 54 periods of immobility during sleep, along with high intensity of stimulus required for arousal, 55 can make an organism vulnerable to predation.…”