Locomotor activity and body temperature patterns over a temperature gradient in the highveld mole-rat (Cryptomys hottentotus pretoriae)

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Authors

Haupt, Meghan
Bennett, Nigel Charles
Oosthuizen, Maria Kathleen

Journal Title

Journal ISSN

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Publisher

Public Library of Science

Abstract

African mole-rats are strictly subterranean mammals that live in extensive burrow systems. High humidity levels in the burrows prevent mole-rats from thermoregulating using evaporative cooling. However, the relatively stable environment of the burrows promotes moderate temperatures and small daily temperature fluctuations. Mole-rats therefore display a relatively wide range of thermoregulation abilities. Some species cannot maintain their body temperatures at a constant level, whereas others employ behavioural thermoregulation. Here we test the effect of ambient temperature on locomotor activity and body temperature, and the relationship between the two parameters, in the highveld mole-rat. We exposed mole-rats to a 12L:12D and a DD light cycle at ambient temperatures of 30ÊC, 25ÊC and 20ÊC while locomotor activity and body temperature were measured simultaneously. In addition, we investigated the endogenous rhythms of locomotor activity and body temperature at different ambient temperatures. Mole-rats displayed nocturnal activity at all three ambient temperatures and were most active at 20ÊC, but least active at 30ÊC. Body temperature was highest at 30ÊC and lowest at 20ÊC, and the daily cycle was highly correlated with locomotor activity. We show that the mole-rats have endogenous rhythms for both locomotor activity and body temperature. However, the endogenous body temperature rhythm appears to be less robust compared to the locomotor activity rhythm. Female mole-rats appear to be more sensitive to temperature changes than males, increased heterothermy is evident at lower ambient temperatures, whilst males show smaller variation in their body temperatures with changing ambient temperatures. Mole-rats may rely more heavily on behavioural thermoregulation as it is more energy efficient in an already challenging environment.

Description

S1 Fig. Soil temperature. Ambient temperatures (ÊC) in full sun, shade and at different soil depths over five consecutive days.
S2 Fig. Daily mean Tb and activity. Mean body temperature (±SE) and mean activity counts (±SE) for female and male highveld mole-rats over the 24h day at each of the three ambient temperatures tested. Black bars indicate the dark phase of the light cycle and white bars indicate the light phase.
S3 Fig. Actograms. Complete actograms for the duration of the experimental procedure are presented for all animals. The black and white bars on top of the actograms shows the dark and light phases during the LD cycles, during DD cycles no light is present. The number of days are on the Y-axis.

Keywords

Mole-rats, Burrows, Body-temperature, Thermoregulatio

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Citation

Haupt M, Bennett NC, Oosthuizen MK (2017) Locomotor Activity and Body Temperature Patterns over a Temperature Gradient in the Highveld Mole-Rat (Cryptomys hottentotus pretoriae). PLoS ONE 12(1): e0169644. DOI:10. 1371/journal.pone.0169644.