Life in an African Alpine Habitat: Diurnal Activity Patterns of the Ice Rat Otomys Sloggetti Robertsi

Hinze, Andrea; Pillay, Neville

doi:10.1657/1523-0430(2006)38[540:liaaah]2.0.co;2

Cited by 18 publications

(16 citation statements)

References 27 publications

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“…In this study, the agouti population was consistently inactive throughout the night, regardless of the mean daily temperature. Similar behaviour has also been observed in other rodent species occupying different habitats (Hinze & Pillay 2006, Ilan & Yom-Tov 1990. Other rodents have the same thermoregulatory strategy, altering their activity peaks as a function of temperature variation, within the same season or between seasons , Kenagy et al 2002, Váczi et al 2006).…”

Section: Activitysupporting

confidence: 72%

The relationship between external temperature and daily activity in a large rodent (Dasyprocta azarae) in the Brazilian Pantanal

2015

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Link to this article: http://journals.cambridge.org/abstract_S0266467415000309How to cite this article: Bruno Cid, Luiz Gustavo R. Oliveira-Santos and Guilherme Mourão (2015). The relationship between external temperature and daily activity in a large rodent (Dasyprocta azarae) in the Brazilian Abstract: Daily activity patterns reflect interactions between circadian mechanisms and environmental stimuli. Among these stimuli, temperature can be an important factor affecting activity budgets. To sample the agouti (Dasyprocta azarae), a systematic camera-trap grid was established with 50 independent sampling sites. A circular kernel function was used to characterize the activity patterns of the agouti population. To evaluate shifts in activity as a function of mean daily temperature, the entire set of records was subdivided into smaller sets covering different temperature ranges. The activity pattern belonging to each set was characterized and compared through the overlap of their full activity (95% isopleth) and activity core (50% isopleth). Based on 400 independent records, agoutis were predominately diurnal. They shifted their activity core, while keeping their activity range (the amount of time a population remains active during the 24-h cycle) constant through the temperature gradient. The agouti demonstrated a unimodal activity pattern at lower temperatures, which became more bimodal at higher temperatures. Nevertheless, it kept its activity range constant, regardless of temperature. These results likely reflect a trade-off between activity time and thermoregulation during the diurnal period and demonstrate how the agouti can change its behaviour to achieve thermal comfort.

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Section: Activitysupporting

confidence: 72%

The relationship between external temperature and daily activity in a large rodent (Dasyprocta azarae) in the Brazilian Pantanal

2015

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“…Ice rats are vulnerable to thermoregulatory stress due to their high surface area to volume ratio, which creates greater heat exchange with the environment (McNab, ). In accordance with the social thermoregulatory hypothesis, ice rats huddle in their burrows (Hinze & Pillay, ), presumably reducing the per capita energy expenditure for thermoregulation (Scantlebury et al ., ).…”

Section: Introductionmentioning

confidence: 75%

“…However, they have morphological adaptations, such as an elongated small intestine for increased energy uptake (Schwaibold & Pillay, ) and thick fur for insulation (Rymer, Kinahan & Pillay, ). Behaviourally, they time their activity to the warmest periods (Hinze & Pillay, ) and bask by withdrawing the limbs, tucking in the head and orientating the back to capture the sun's rays (Rymer et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Spatial dichotomy of sociality in the African ice rat

2013

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Sociality is environmentally and phylogenetically determined and can vary intraspecifically and interspecifically. We investigated the reasons for group living in the African ice rat Otomys sloggetti robertsi, a diurnal, herbivorous, nonhibernating murid rodent, endemic to the sub-alpine and alpine regions of the southern African Drakensberg and Maluti mountains. We expected ice rats to be group living, nesting communally in underground burrows. We documented the spatial organization and social behaviour of free-living ice rats through direct observations and experimental manipulations. Colonies comprised 4-17 adults of both sexes. Members of a colony had a high degree of spatial home-range overlap but no temporal overlap because interactions between members were rare aboveground. Individuals experimentally displaced within their own colony were attacked by members of their own colony and were treated in the same way as strangers from other colonies. Members of a colony competed aggressively for prized food, particularly in winter. Ice rats displayed a vertical spatial separation in social behaviour, from huddling and tolerance belowground to solitary foraging and mutual avoidance aboveground. Such a dichotomy in sociality reflects the compromise between the benefits of social thermoregulation and burrow sharing on the one hand and the constraints of competing for resources, mainly food, on the other. Such a compromise may ultimately be related to the poor physiological adaptation of ice rats to the cold environments they inhabit.

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“…These were carefully excavated with a spatula and a small shovel so as to maintain the original organisation of tunnels and associated structures. Before excavations were started, the inhabitants occupying the burrow system were counted using instantaneous scan sampling every 5 min when aboveground activity levels within a colony were highest (i.e., early morning and late afternoon; Hinze and Pillay 2006). The occupants within the burrow system most likely moved into neighbouring systems when excavations were started.…”

Section: Methodsmentioning

confidence: 99%

“…To cope with thermal stress, O. s. robertsi employs behavioural (sun-basking, huddling) and morphological (dense fur, short extremities, modified gut) adaptations (Willan 1990;Schwaibold and Pillay 2003). Moreover, ice rat colonies have numerous burrow holes, and it is likely that the burrow system of ice rats functions as a thermal buffer against climatic extremes, since ice rats retreat into burrows during the coldest and hottest times of the day (Hinze and Pillay 2006). The ice rat belongs to the subfamily Otomyinae (Family: Muridae), a group of herbivorous rodents that is widely distributed across the primarily east-west southern African rainfall gradient (Skinner and Smithers 1990).…”

Section: Introductionmentioning

confidence: 99%

The burrow system of the African ice rat Otomys sloggetti robertsi

2006

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We studied the architecture of the burrow system of the African ice rat Otomys sloggetti robertsi, a non-hibernating, diurnal murid rodent endemic to the sub-alpine and alpine regions of the southern African Drakensberg and Maluti mountains. In our study site we found ice rat burrows in two substrates (organic and mineral soils). The structure of the burrow system was similar in both soil types, comprising several interlinking tunnels, numerous burrow entrances and 1-2 nest chambers. However, the surface area of the burrow systems in organic soils was larger, the tunnels were deeper, and some of the systems contained two levels, all of which was contrary to our assumption that digging would be more difficult in the compact organic soils. Ice rats occur in colonies of up to 17 individuals, and the collected efforts of several individuals are required for constructing complex burrow systems. The burrow structure is similar to those of two arid-adapted relatives, Parotomys brantsii and Parotomys littledalei, suggesting that the burrow architecture among these three taxa may reflect the similar functions of burrows in extreme environments. For ice rats, burrows could provide a suitable microhabitat in which to escape adverse environmental conditions, particularly during winter. Moreover, ice rat burrows contained far fewer nest chambers than those of both Parotomys species, indicating that members in a colony share nest chambers, thereby facilitating huddling. Finally, the extensive interlinking tunnels may provide underground routes to aboveground feeding sites, thereby reducing exposure to adverse conditions.

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Life in an African Alpine Habitat: Diurnal Activity Patterns of the Ice Rat Otomys Sloggetti Robertsi

Abstract: BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Cited by 18 publications

References 27 publications

The relationship between external temperature and daily activity in a large rodent (Dasyprocta azarae) in the Brazilian Pantanal

The relationship between external temperature and daily activity in a large rodent (Dasyprocta azarae) in the Brazilian Pantanal

Spatial dichotomy of sociality in the African ice rat

The burrow system of the African ice rat Otomys sloggetti robertsi

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