Thermoregulation in three southern African bat species inhabiting a hot, semi-arid environment

Bats inhabiting arid, subtropical environments face diverse challenges related to energy and water balance. First, they may have to conserve water and energy during cool, dry winters when water is scarce and insect availability reduced. Second, during hot summers when air temperature may routinely exceed body temperature, bats may need to avoid both hyperthermia and dehydration. A common response to the energetically challenging winter period in temperate, subtropical and tropical species is heterothermy (i.e. torpor and hibernation). Despite evidence suggesting that heterothermy is of major significance in the energy balance of tropical and subtropical bats, its occurrence in southern African species especially those in semi-arid subtropical regions have received relatively little attention. Moreover, the physiological and thermoregulatory responses of bats to high air temperatures (Ta) are relatively poorly known. The goal of my project was to investigate various seasonal physiological challenges imposed on bats in an arid, sub-tropical climate. I investigated the occurrence of winter heterothermy in Nycteris thebaica (Nycteridae) in the Limpopo Valley. Skin temperatures (Tskin) were measured using temperature-sensitive transmitters, and roost temperatures (Troost) were recorded using miniature temperature loggers. N. thebaica used multiple roosting sites, including a hollow baobab tree (Adansonia digitata) and several caves, and exhibited only moderate heterothermy. Tskin was maintained around normothermic levels, with differences of 3-9°C (7.5±1.7°C) between overall maximum and minimum Tbs. A minimum Tskin of 28.4°C occurred at Troost = 23.8°C, and patterns of thermoregulation did not appear to be influenced by prevailing weather conditions. Roost temperatures did not decrease below 10°C, and averaged 21.2±2.8°C and 23.3±2.9°C respectively. The lack of pronounced heterothermy in N. thebaica is surprising, particularly in view of the daily torpor cycles observed in many insectivorous bat species. I also investigated the physiological responses of three sympatric bat species during summer using an open-flow respirometry system to measure resting metabolic rates (RMR) and evaporative water loss (EWL) over a range of Tas ~ 10-42°C, with body temperatures (Tb) simultaneously recorded via temperature-sensitive passive integrated transponder (PIT) tags. Basal metabolic rates for Nycteris thebaica and Taphozous mauritianus were 8.9±2.7mW.g-1 and 6.6±2.2mW.g-1 respectively, falling within the 95% prediction intervals for bat BMR, whereas the value for Sauromys petrophilus (3.4±0.6mW.g-1) fell below the lower 95% prediction interval. Maximum EWL for N. thebaica, T. mauritianus and S. petrophilus were 18.6±2.1mg.g-1.h-1 (Ta=39.4°C), 14.7±3.1mg.g-1.h-1 (Ta=41.9°C) and 23.7±7.4mg.g-1.h-1 (Ta=41.7°C) respectively. Maximum individual Tbs recorded were 46.5°C in N. thebaica (Ta=39.3°C), 44.9°C in T. mauritianus (Ta=41.8°C) and 46.5°C in S. petrophilus (Ta=41.7°C). Overall, I found that N. thebaica was the least heat tolerant species, with T. mauritianus and S. petrophilus being more heat tolerant. In the face of climate change, heat tolerance together with specific thermal properties of a given roost may play a major role in the ability of a species to persist in a hot, arid environment.Dissertation (MSc)--University of Pretoria, 2012.Zoology and Entomologyunrestricte

Interspecific variation in thermoregulation among three sympatric bats inhabiting a hot, semi-arid environment

Bats in hot roosts experience some of the most thermally challenging environments of any endotherms, but little is known about how heat tolerance and evaporative cooling capacity varies among species. We investigated thermoregulation in three sympatric species (Nycteris thebaica, Taphozous mauritianus, and Sauromys petrophilus) in a hot, semi-arid environment by measuring body temperature (Tb), metabolic rate and evaporative water loss (EWL) at air temperatures (Ta) of 10 - 42 °C. S. petrophilus was highly heterothermic with no clear thermoneutral zone, and exhibited rapid increases in EWL at high Ta to a maximum of 23.7 ± 7.4 mg g-1 hr-1 at Ta ≈ 42 °C, with a concomitant maximum Tb of 43.7±1.0 °C. T. mauritianus remained largely normothermic at Tas below thermoneutrality, and increased EWL to 14.7 ± 1.3 mg g-1 hr-1 at Ta ≈ 42 °C, with a maximum Tb of 42.9 ± 1.6 °C. In N. thebaica, EWL began increasing at lower Ta than in either of the other species, and reached a maximum of 18.6±2.1 mg g-1 hr-1 at Ta = 39.4 °C, with comparatively high maximum Tb values of 45.0±0.9°C. Under the conditions of our study, N. thebaica was considerably less heat tolerant than the other two species. Among seven species of bats for which data on Tb as well as roost temperatures in comparison to outside Ta are available, we found limited evidence for a correlation between overall heat tolerance and the extent to which roosts are buffered from high Ta.This study was facilitated by funding from Bat Conservation International, the National Research Foundation and the University of Pretoria.http://www.springer.com/life+sci/biochemistry/journal/360hb2013ab201

Thermoregulation in free-ranging Nycteris thebaica (Nycteridae) during winter : no evidence of torpor

Bats are among the most heterothermic mammals, with nearly all species investigated under free-ranging conditions to date exhibiting some degree of daily torpor and/or hibernation. We investigated thermoregulation during late winter by seven Nycteris thebaica in a warm, semi-arid habitat in northern South Africa, using temperature-sensitive transmitters to measure skin temperature (Tskin). Unexpectedly, we found no evidence for any expression of daily torpor or hibernation based on a total of 86 days of data from 7 bats (one male and six females), despite air temperatures as low as ∼10 ◦C. Instead, daytime Tskin was distributed unimodally with most values in the 33–35 ◦C range, and a minimum Tskin of 28.4 ◦C at a roost temperature of 24.6 ◦C. There are several possible reasons why N. thebaica may avoid torpor, including predation in roosts, and the long nightly foraging periods of this species compared to many others.http://www.elsevier.com/locate /mambiohb201

A burning question: what are the risks and benefits of mammalian torpor during and after fires?

Although wildfires are increasing globally, available information on how mammals respond behaviourally and physiologically to fires is scant. Despite a large number of ecological studies, often examining animal diversity and abundance before and after fires, the reasons as to why some species perform better than others remain obscure. We examine how especially small mammals, which generally have high rates of energy expenditure and food requirements, deal with fires and postfire conditions. We evaluate whether mammalian torpor, characterised by substantial reductions in body temperature, metabolic rate and water loss, plays a functional role in survival of mammals impacted by fires. Importantly, torpor permits small mammals to reduce their activity and foraging, and to survive on limited food. Torpid small mammals (marsupials and bats) can respond to smoke and arouse from torpor, which provides them with the possibility to evade direct exposure to fire, although their response is often slowed when ambient temperature is low. Post-fire conditions increase expression of torpor with a concomitant decrease in activity for free-ranging echidnas and small forest-dwelling marsupials, in response to reduced cover and reduced availability of terrestrial insects. Presence of charcoal and ash increases torpor use by captive small marsupials beyond food restriction alone, likely in anticipation of detrimental post-fire conditions. Interestingly, although volant bats use torpor on every day after fires, they respond by decreasing torpor duration, and increasing activity, perhaps because of the decrease in clutter and increase in foraging opportunities due to an increase in aerial insects. Our summary shows that torpor is an important tool for post-fire survival and, although the physiological and behavioural responses of small mammals to fire are complex, they seem to reflect energetic requirements and mode of foraging. We make recommendations on the conditions during management burns that are least likely to impact heterothermic mammals

Satellite Tagging and Biopsy Sampling of Killer Whales at Subantarctic Marion Island: Effectiveness, Immediate Reactions and Long-Term Responses

Remote tissue biopsy sampling and satellite tagging are becoming widely used in large marine vertebrate studies because they allow the collection of a diverse suite of otherwise difficult-to-obtain data which are critical in understanding the ecology of these species and to their conservation and management. Researchers must carefully consider their methods not only from an animal welfare perspective, but also to ensure the scientific rigour and validity of their results. We report methods for shore-based, remote biopsy sampling and satellite tagging of killer whales Orcinus orca at Subantarctic Marion Island. The performance of these methods is critically assessed using 1) the attachment duration of low-impact minimally percutaneous satellite tags; 2) the immediate behavioural reactions of animals to biopsy sampling and satellite tagging; 3) the effect of researcher experience on biopsy sampling and satellite tagging; and 4) the mid- (1 month) and long- (24 month) term behavioural consequences. To study mid- and long-term behavioural changes we used multievent capture-recapture models that accommodate imperfect detection and individual heterogeneity. We made 72 biopsy sampling attempts (resulting in 32 tissue samples) and 37 satellite tagging attempts (deploying 19 tags). Biopsy sampling success rates were low (43%), but tagging rates were high with improved tag designs (86%). The improved tags remained attached for 26±14 days (mean ± SD). Individuals most often showed no reaction when attempts missed (66%) and a slight reaction-defined as a slight flinch, slight shake, short acceleration, or immediate dive-when hit (54%). Severe immediate reactions were never observed. Hit or miss and age-sex class were important predictors of the reaction, but the method (tag or biopsy) was unimportant. Multievent trap-dependence modelling revealed considerable variation in individual sighting patterns; however, there were no significant mid- or long-term changes following biopsy sampling or tagging

The potential of bats as bioindicators for areas currently transformed by opencast mining within the Vhembe Biosphere Reserve, Limpopo Province, South Africa.

PhD (Zoology)Department of ZoologyBats are the second most diverse order of mammals and provide crucial ecosystem services from insect control (including significant crop pest species), to pollination of plants and seed dispersal. Bats are known to be sensitive to alterations in their environment. Globally, bat populations and communities are under pressure due to anthropogenic activities that alter their natural habitats creating unfavourable habitats for some bat species and favourable conditions for others. Anthropogenic activities, impose a multitude of impacts on bats such as artificial lighting throughout nocturnal periods and excessive noise during both diurnal and nocturnal periods. These alterations of habitats affect bat roosting and emergence behaviour, disrupt commuting routes to foraging grounds and alter interspecific competition. Additionally, bats are exposed to and suffer physiological issues relating to contaminants such as heavy metals and trace elements of which their liberation is exacerbated by human activities. African bat conservation is already under considerable pressure from the development occurring throughout the continent. A looming development of significant concern is the proposed African Mining Vision to develop mining and transport networks throughout sub-Saharan Africa. The fate of bat conservation in Africa is dependent on bat taxonomy (with new species regularly described), an understanding of African bat ecology and the responses of bat species to changes in their environment. Research covering these aspects are greatly needed in order to propose environmental mitigation and remediation strategies. Bats have the potential as bioindicators to provide information concerning ecosystem health pre-, during and post- large scale developments such as mining. My study focused on how a bat community in northern Limpopo Province was impacted by the de Beers Venetia opencast diamond mining operation. I investigated which bat species have the potential to be bioindicators based on the impact of habitat degradation (Chapter 2). The impact of artificial light and anthropogenic noise was explored (Chapter 3) and the use of bat fur and blood as biomarkers of bat exposure to heavy metals and trace elements (Chapter 4). Bats have the potential to be good bioindicators as they are easy to monitor in areas like mines that are often a challenge to access and or have high safety risks due to heavy machinery movement and human exposure to possible environmental contaminants. By using passive acoustic recording techniques, the composition and activity of the bat community was determined on the Venetia diamond mine and over the natural areas neighbouring the mine. Six bat detectors were deployed for a full summer and winter season to determine what factors (both anthropogenic and natural) influenced total bat activity as well as species richness and diversity. The effect of habitat type (natural habitats Musina Mopane Bushveld and Limpopo Ridge Bushveld vs altered landscapes of the wastewater dam and opencast pit), season, minimum temperature (Tmin) and moon phase were investigated. Habitat type and season were shown by the best-fit models to be the main factors affecting bat activity, which was lower during winter and consistently lower over the heavily disturbed opencast mining pit. It was evident from the passive acoustic recordings of echolocation calls that the Venetia diamond mine was an important resource for numerous bat species, particularly at the wastewater dam, boasting ~18 out of 22 species/species groups. The wastewater dam provided a sought after resource for foraging and possibly drinking by bats. The infrastructure of the mine was also observed to be used by molossid bats as roosting opportunities. Based on the clear-cut response of three species/species groups to habitat type, Laephotis capensis/Pipistrellus (Vansonia) rueppellii, Afronycteris nana and Pipistrellus rusticus/Neoromicia anchietae were proposed as bioindicators on the Venetia diamond mine. All three species/species groups could be environmental indicators which means that they respond to physical changes in the environment, in this case, changes in preferred habitat. Laephotis. capensis/P. rueppellii generally avoided the mining footprint and were abundant in the natural areas whereas A. nana and P. rusticus/N. anchietae were prolific over the wastewater dam, particularly during winter. The response of A. nana and P. rusticus/N. anchietae may be a reflection of changes in insect species composition over the wastewater dam in relation to potential changes in water quality and as such, have also been suggested as ecological indicators as they may be reflecting the change in another taxon or group (invertebrates). Further research in this regard is required. Bat species were characterised as exploiters and adapters to resources provided by the mine such as new artificial roosting opportunities in infrastructure and resource creation, particularly artificial water sources that would otherwise be scarce for bats in the semi-arid environment. Examples of these exploiter and adapter species were Chaerephon pumilus/Mops condylurus that exploited resources provided by the mine from roosting in buildings to using the wastewater dam, and P. hesperidus as an adapter that used the wastewater dam as an important resource particularly during winter and was only recorded in natural areas during summer but is not known to roost in the infrastructure of the mine. Even though the mining activities provided resources, bats were exposed to continuous anthropogenic noise and artificial light during their night-time foraging period. To investigate the impacts of anthropogenic noise and artificial lighting, a transect was installed on the Venetia diamond mine using six SM4BAT acoustic recorders (bat detectors) (Wildlife acoustics, Inc.) to passively record bat species and their associated activity. The transect began in a brightly lit area near some workshops and a conveyor belt system and extended past the well-lit and noisy processing plant, into an open-air laydown storage area and terminated in natural vegetation. Surprisingly, according to mixed-effects models, in general, anthropogenic noise did not have a significant impact on bat activity or species richness. Artificial light only negatively impacted foraging activity and there was little evidence of bats foraging under the floodlights near the workshop and processing plant. Artificial light may possibly impact total bat activity and searching/commuting behaviour. In support of the data concerning the lowest bat activity and species richness over the habitat devoid pit of the mine, the percentage of natural vegetation cover was the most important factor influencing all bat activity and species richness. With significant bat activity recorded over the mine wastewater dam, there is potential for bats to be exposed to high concentrations of contaminants, particularly heavy metals and trace elements that would otherwise be naturally occurring at lower concentrations in the environment. Therefore, I investigated the potential bioaccumulation of elements in molossid bats from the mining footprint and in a control area adjacent to the mine. There is great interest in using bats as bioindicators of environmental contaminants and with a focus on non-lethal and less invasive methodologies, the fur and blood of several Tadarida aegyptiaca and C. pumilus/M. condylurus was tested for 23 elements. Fur is a good indicator of exposure to elements over an extended period and blood provides insight into more recent exposure. Fifteen of the 22 elements (barium excluded as it was predominantly below detection limits), were higher in the fur that in the blood samples. Concentrations of boron (B), potassium (K), rubidium (Rb) and cadmium (Cd) in fur and zinc (Zn), and mercury (Hg) in blood were significantly higher in samples from the opencast diamond mine compared with the control site. Manganese (Mn) was higher in the blood of bats from the control site than from the mine. Although weak, the only significant correlations between fur and blood element concentrations were found for Hg and strontium (Sb). Comparative data with other bat species is scant in the literature and there are currently no toxicological thresholds for elements in bats, thus the low concentrations of most elements, except aluminium (Al), iron (Fe) and Zn, may reflect background values. These data are the first presented to compare blood and fur elemental concentrations of South African bats the implications of which are currently unknown. 3 These data presented in my thesis has great potential to add to the environmental monitoring of the Venetia diamond mine by providing insight into trends in the bat population (including species richness) that utilise the mine associated (drinking and foraging areas over the waste water dams, and roosting opportunities in mine infrastructure). These data can be used as a baseline to monitor the current and future environmental impacts of the mine as production continues and, can be used to monitor and assist rehabilitation efforts soon to be underway.NR

Heterothermy in free-ranging male Egyptian Free-tailed bats (Tadarida aegyptiaca) in a subtropical climate

No abstract availabl

Selection criteria for multievent capture recapture models of sighting histories of killer whales at Marion Island: long-term (up to 24 months) responses following sampling (tagging or biopsy) attempts.

<p>‘Season’ refers to the same seasonality affect for all individuals. ‘DH(1).season’ refers to seasonality applying only to one of two hidden mixture groups (suggesting ‘resident’ and ‘migrant’ animals) while ‘DH(2).season’ refers to seasonality applying to all individuals but independently for two hidden groups (suggesting variation between individuals). ‘trap’ refers to a trap-dependence effect, ‘sampling’ refers to a sampling effect and ‘t_{2008–2011;2011–2013}’ accounts for two periods with differing field effort.</p><p>Notes: ^aĉ = 1.75.</p><p>Selection criteria for multievent capture recapture models of sighting histories of killer whales at Marion Island: long-term (up to 24 months) responses following sampling (tagging or biopsy) attempts.</p

Model selection for the generalized linear models (GL Ms) used to describe factors influencing the probability of hitting the target animal (<i>hit/miss</i>) during a sampling attempt.

<p>The full model was <i>hit/miss ∼experience + biopsy/tag + range + arbalester</i>. Only the predictor variables included in each model are shown.</p><p>Notes: ^anumber of parameters; ^bsmall sample corrected Akaike Information Criterion; ^cdifference between the AIC_c score of the model in question and the best model; ^dAkaike weight: relative likelihood of model in question divided by the sum of relative likelihoods for all models.</p><p>Model selection for the generalized linear models (GL Ms) used to describe factors influencing the probability of hitting the target animal (<i>hit/miss</i>) during a sampling attempt.</p