Varanus flavescens (yellow monitor): Thermoregulation

Eight \yater monitor lizards. l'arallllS s, sa/ wror. were captured: four individuals from an oil palm estate on the :Vlalayan peninsula. and four from fresh water-deficient Tulai island 65 km off-shore in the South Chma Sea, They were fined with a radio trans mitter attached to a thermistor which was inserted into the cloaca of the animals and released. The heating rate during basking was measured as 0.117 and 0.118 vC' min -; while the daily cloacal temperature fluctuated between 29.5-37.3

Copeia, 1992

The Forestry Chronicle, 2012

Throughout the world, population growth and conversion of land for human development increase the potential for areas of human and wildlife activity to overlap. Anthropogenic effects on animal behavior may have ecological consequences if response to human disturbance or dependence on anthropogenic food sources prevents wildlife from carrying out traditional ecological roles. The presence of large predatory species such as the water monitor lizard, Varanus salvator, in areas of human development may also result in conflict if animals become habituated to the presence of humans or begin to compete for resources. Understanding anthropogenic effects on V. salvator resource use and activity is a key to predicting behavior and informing conflict mitigation in systems where humans and V. salvator coexist. V. salvator home ranges and resource use will be investigated on Tinjil Island, Indonesia, where radiotelemetry will be used to track V. salvator individuals across areas of varying human presence in both wet and dry seasons. Greater insight into anthropogenic influences on V. salvator resource use will contribute increased knowledge of V. salvator's ecological role in undisturbed and human-altered communities and can serve to inform the prevention of human-V. salvator conflict.

Journal of Thermal Biology, 2016

We studied, at 2200 m altitude, the thermal biology of the Pyrenean rock lizard, Iberolacerta bonnali, in glacial cirque of Cotatuero (National Park of Ordesa, Huesca, Spain). The preferred thermal range (PTR) of I. bonnali indicates that it is a coldadapted ectotherm with a narrow PTR (29.20-32.77 °C). However, its PTR (3.57 °C) is twice as wide as other Iberolacerta lizards, which may be explained by its broader historical distribution. The studied area is formed by a mosaic of microhabitats which offer different operative temperatures, so that lizards have, throughout their entire daily period of activity, the opportunity to choose the most thermally suitable substrates. I. bonnali achieves an effectiveness of thermoregulation of 0.95, which makes it the highest value found to date among Lacertidae, and one of the highest among lizards. Their relatively wide distribution, their wider PTR, and the excellent ability of thermoregulation, would make I. bonnali lizards less vulnerable to climate change than other species of Iberolacerta. Thanks to its difficult access, the studied area is not visited by a large number of tourists, as are other areas of the National Park. Thus, it is a key area for the conservation of the Pyrenean rock lizard. By shuttling between suitable microhabitats, lizards achieve suitable body temperatures during all day. However, such thermally suitable microhabitats should vary in other traits than thermal quality, such as prey availability or predation risk. Hence, it seems that these not-thermal traits are not constraining habitat selection and thermoregulation in this population. Therefore, future research in this population may study the causes that would lead lizards to prioritize thermoregulation to such extent in this population.

Observations were made on the behaviour and body temperatures of the legless lizard Anguis fragilis when active above ground in outdoor enclosures. The lizards were most frequently observed in partially shaded locations followed by fully shaded areas; full basking and locomotory movement were minor activities irrespective of weather conditions. Weather conditions had no significant influence on behaviour. Tests for thermoregulation using null models indicated that the main reason for movement above ground was thermoregulatory. Body temperatures were significantly higher than shade operative temperatures but lower than operative temperatures in open locations whatever the weather. Standard deviations in body temperature, employed as a measure of thermoregulatory precision, were lower than standard deviations of operative temperatures in sunny weather but not significantly different from operative temperatures during overcast weather or shaded operative temperatures during sunny weather. The limited amount of locomotory movement suggests thermoregulation was achieved through selection of appropriate microenvironments.

Canadian Journal of Zoology, 2002

Behavioural regulation of body temperature in thermally heterogeneous habitats requires different amounts of time that could otherwise be dedicated to foraging and social activities. In this study I examined how four populations of the lizard Zootoca vivipara along an altitudinal gradient (250–1450 m) adjust their thermal-physiology traits and thermoregulatory behaviour to compensate for increasing time costs of thermoregulation. I focused on variation in several physiological (set-point temperature, heating rate) and behavioural traits (microhabitat selection, basking frequency, extent of thermoregulation). To estimate potential time spent basking and foraging by lizards that were not employing any behavioural compensatory mechanism, I used a simple biophysical model of thermoregulation, including information about operative temperatures at the study sites, selected temperature range, and heating/cooling rates. Time costs of thermoregulation for each population were calculated as potential time spent basking relative to time spent foraging. Operative temperatures varied among study sites, resulting in different time costs of thermoregulation. Lizards at 1450 m should spend about 50% more time basking than those at 250 m. I found that the only mechanism which potentially compensated for the higher time costs incurred at high altitudes was a shift in the choice of basking sites.Lizards thermoregulated with similar accuracy and effectiveness over the 1200-m altitudinal range, indicating that there were no adjustments in the extent of thermoregulation. The observed basking frequencies of lizards were highly correlated with potential time spent basking without behavioural adjustments, suggesting a minor compensatory effect of thermoregulatory behaviour. Lizards responded to higher time costs of thermoregulation primarily by allocating different amounts of time to basking. These results suggest that Z. vivipara regulated body temperature at the expense of time that could be devoted to other activities.

Studies on Neotropical Fauna and Environment, 1996

2013

Aim Temperature influences most components of animal ecology and life history–but what kind of temperature? Physiologists usually examine the influence of body temperatures, while biogeographers and macroecologists tend to focus on environmental temperatures. We aim to examine the relationship between these two measures, to determine the factors that affect lizard body temperatures and to test the effect of both temperature measures on lizard life history.

2019

Temperature has a significant influence on physiology, ecology, and life history of ectotherms. Despite environmental fluctuations, lizards have developed behavioral mechanisms to maintain a relatively constant body temperature. These behaviors are particularly important for lizards living at high elevations like the high mountain lizard Phymaturus palluma, an endemic lizard to Central Andes. We studied how this species thermoregulates throughout the day and how abiotic and biophysical factors influence their activity. We recorded lizard activity and body postures and orientations at different times of the day during two seasons. Results indicate that P. palluma invest most of their time and energy in thermoregulation to maintain an optimal body temperature. Lizards activity raised with operative temperature of sun-exposed rocks up to an optimum and declined above that temperature. In addition, activity was negatively correlated with crevice temperature and positively correlated with mean operative temperature. Lizards changed their heat source along the day, using heliothermy most part of daytime and thigmothermy in the afternoon. Body postures were related to operative temperatures, so they may play an important role in thermoregulation. In contrast, body orientations were not related to operative temperatures. This study supports the idea that the benefit of thermoregulatory behaviors exceeds the energetic costs and the risk of predation involved in basking activities.

Varanus olivaceus, butaan as it is known locally, has been an enigmatic creature to the scientific community, avoiding detection by many competent biologists for 130 years. Until the monumental works of Auffenberg in the 1970s, and most recently Bennett, almost nothing was known of this lizard's biology. We now understand it is one of three documented highly arboreal and primarily frugivorous monitors, all of which are endemic to the Philippines. Specimens of this shy species have trickled into captive collections through legal and illegal means since its rediscovery in 1976. Due to its specialized lifestyle, captive specimens have proven difficult keep let alone reproduce. The Los Angeles Zoo has worked almost continuously with butaan since 1998, when four specimens were seized by the United States Fish and Wildlife Service and transferred to the Zoo. In 2015, the Zoo's work culminated in the first successful hatching of four offspring. A second clutch of eight fertile eggs produced five additional hatchlings in 2015. The Los Angeles Zoo has utilized many strategies, both typical and unusual, to induce reproduction, incubate eggs, and raise young butaan. The following details the husbandry techniques used to keep and reproduce this rare species.