Mark Brigham

Permanent URI for this collectionhttps://hdl.handle.net/10294/8900

Professor

Office: LB 242
E-mail: Mark.Brigham@uregina.ca
Phone: 306-585-4255 or 306-585-4562
Fax: 306-337-2410

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Open Access
Cold and alone? Roost choice and season affect torpor patterns in lesser short‑tailed bats
(Springer, 2017) Brigham, R. Mark; HIckey, Anthony J.R.; Parsons, Stuart; Czenze, Zenon J.
Seasonal changes in weather and food availability differentially impact energy budgets of small mammals such as bats. While most thermal physiological research has focused on species that experience extreme seasonal temperature variations, knowledge is lacking from less variable temperate to subtropical climates. We quantified ambient temperature (Ta) and skin temperature (Tsk) responses by individuals from a population of New Zealand lesser shorttailed bats (Mystacina tuberculata) during summer and winter using temperature telemetry. During summer, communal roosts were more thermally stable than Ta. During winter, solitary roosts were warmer than Ta indicating significant thermal buffering. Communal roost trees were used on 83 % of observation days during summer, and individuals occupying them rarely entered torpor. Solitary roosts were occupied on 93 % of observation days during winter, and 100 % of individuals occupying them used torpor. During summer and winter, bats employed torpor on 11 and 95 % of observation days, respectively. Maximum torpor bout duration was 120.8 h and winter torpor bout duration correlated negatively with mean Ta. Torpor bout duration did not differ between sexes, although female minimum Tsk was significantly lower than males. The summer Heterothermy Index varied, and was also significantly affected by Ta. Mean arousal time was correlated with sunset time and arousals occurred most frequently on significantly warmer evenings, which are likely associated with an increased probability of foraging success. We provide the first evidence that torpor is used flexibly throughout the year by M. tuberculata, demonstrating that roost choice and season impact torpor patterns. Our results add to the growing knowledge that even small changes in seasonal climate can have large effects on the energy balance of small mammals.
Open Access
Quantifying Relative Levels of Solar Radiation at Bat Roosts Using Pyranometers
(Wiley - The Wildlife Society, 2017) Bondo, Kristin J.; Brooks, David R.; Brigham, R. Mark
Although the amount of solar radiation received at roost sites used by bats has been speculated to be a factor driving roost-site selection and roost switching behavior, few studies have scientifically quantified and recorded it over time. We demonstrated through a field test how silicon-cell pyranometers, which are commonly connected to dataloggers and used in atmospheric studies to measure solar irradiance on a planar surface, can also be used to measure and record relative solar radiation levels at roost trees used by bats and other wildlife. Using commercially available pyranometers might not be feasible for many wildlife studies because they are expensive; we demonstrate how they can be built relatively simply and inexpensively, and calibrated with a commercial silicon-cell pyranometer.
Open Access
Stressful summers? Torpor expression differs between high- and low-latitude populations of bats
(American Society of Mammalogists, 2017) Czenze, Zenon J,; Brigham, R. Mark; Hickey, Anthony J.R.; Parsons, Stuart
Variation in weather and food availability impacts the energy budgets of endotherms, with some species using torpor as an energy-saving strategy during periods of negative energy balance. We evaluated how latitudinal differences in energy balance relate to variation in torpor expression and roosting sociality between populations. We monitored summer skin temperatures (Tsk) of individuals from 2 populations of New Zealand lesser shorttailed bats (Mystacina tuberculata) separated by 6° of latitude using temperature telemetry. Although mean summer Ta was only < 1°C lower for the higher-latitude than lower-latitude population, individuals living at the higher-latitude site used torpor on 36% of observation days compared to 11% for lower-latitude bats. None of the recorded weather variables affected the propensity to enter torpor or torpor bout duration; however, the minimum torpid Tsk of bats positively correlated with daily minimum Ta. Roosts occupied by solitary bats were warmer than Ta, and temperatures within them fluctuated less than Ta. Higher-latitude individuals roosted solitarily (38%) more frequently than lower-latitude individuals (17%) and individuals from both populations exclusively used torpor while roosting solitarily. Arousals from torpor by higher-latitude bats coincided with sunset and not daily Ta maxima suggesting that bats were not fully exploiting advantages of passive rewarming. Site-specific roost choice and torpor patterns were apparent between M. tuberculata populations during summer, demonstrating that small differences in Ta differentially affect energetic strategy. The thermoregulatory behavior of species inhabiting latitudinal gradients in climate is highly plastic, likely to meet the specific challenges of their environment.
Open Access
Thermoregulation by captive and free-ranging Egyptian rousette bats (Rousettus aegyptiacus) in South Africa
(American Society of Mammalogists, 2017) Barclay, Robert M.R.; Jacobs, David S.; Harding, Craig T.; McKechnie, Andrew E.; McCulloch, Stuart D.; Markotter, Wanda; Paweska, Janusz; Brigham, R. Mark
Many bats, including some small-bodied tropical and subtropical Pteropodidae, use torpor to offset energetic constraints. We tested the hypothesis that medium-sized (110–160 g) cave-roosting Egyptian rousette bats (Rousettus aegyptiacus) at the southern extent of their range are able to employ torpor. We measured daytime body temperatures (Tb) of 9 wild individuals using implanted temperature-sensitive radiotransmitters. The bats roosted in a cave on Table Mountain, Cape Town, South Africa (a typically cool and wet area). Daily mean cave temperature (Tc) ranged between 7°C and 12°C (mean 9.3°C). All wild individuals exhibited a circadian cycle in Tb, with an average of 37.7°C upon return from foraging, decreasing to 35.5°C by mid-day. Before emergence for feeding, Tb increased to about 37°C. No individual allowed Tb to drop below 34°C indicating (assuming a threshold temperature of 30°C) that individuals in this population do not use torpor. Bats were active throughout the day within the roost and metabolic heat production may have contributed to the maintenance of rest-phase Tb. Ten individuals implanted with temperature-sensitive passive integrated transponder tags were held in captivity at temperatures of 25–30°C and subjected to food deprivation for 2–3 days. The lowest Tb recorded for any captive individual was 33.4°C despite losing an average of 10% of their initial body mass. Despite exposure to cool Ta in the cave, and often cold, wet, and windy conditions while foraging, or substantial food restriction in captive bats, R. aegyptiacus did not resort to using torpor.
Open Access
Winter climate affects torpor patterns and roost choice in New Zealand lesser short-tailed bats
(Wiley-Blackwell (Zoological Society of London), 2017) Czenze, Zenon J.; Brigham, R. Mark; Hickey, Anthony J.R.; Parsons, Stuart
Variation in winter conditions differentially impacts thermoregulation of endotherms, with some species using torpor as an energy-saving strategy during periods of negative energy balance. We evaluated how differences in energy balance due to winter ambient temperatures (Ta), would lead to differing torpor expression and roost choice between populations. Here, we monitored Ta and skin temperatures (Tsk) of New Zealand lesser short-tailed bats (Mystacina tuberculata) using temperature telemetry from an inland population from Pureora, North Island and another from Hauturu/Little Barrier Island (Hauturu), an offshore island. Relative to Pureora, all recorded Ta variables were higher in Hauturu. Hauturu bats used short torpor (<24 h) more frequently (51% of observational days) than their Pureora conspecifics (33%). Furthermore, minimum Tsk of Hauturu bats correlated positively with mean Ta and Hauturu bats were more likely to arouse on nights with warmer sunset Ta. No correlation was found for Pureora bats. Torpor bout duration did not differ between sites. On Hauturu, bats preferred thermally unstable roosts and preferentially roosted inside dead punga/silver fern-trees (Cyathea dealbata). As punga thermal characteristics did not differ from Ta, Hauturu bats may take advantage of warm Ta to reduce rewarming costs. We did not observe differences in any thermoregulatory variables between sexes in Hauturu. Differences in winter Ta may differentially impact populations across a latitudinal gradient. Although bat populations in warmer climates are under less thermoregulatory stress, site and climate specific adaptations appear to be employed that affect roost choice and torpor patterns.

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