Ground pangolins Smutsia temminckii are inconspicuous, mainly nocturnal mammals
that occur at low population densities. As a result, there is scant information available
on the ecology and physiology of this species. To date the handful of studies
focussing on this species were centred in the mesic eastern regions of its range, with
no attention being given to ecological and biological traits in arid environments. To
address these data shortfalls, a study was undertaken in the Kalahari Desert in northwestern
South Africa. Very High Frequency (VHF) transmitters or Global Positioning
System (GPS) loggers were fitted to 16 ground pangolins and their ecology and
physiology studied over a period of three years.
Throughout its range the ground pangolin is increasingly endangered, predominantly
due to anthropogenic threats. Previous studies have identified threats facing this
species, but very few of these studies included quantitative data as to the extent of
these threats. The present study suggests that the main threats to ground pangolins
in southern Africa are electrocution on electrified fences, the traditional medicine
trade, habitat loss, road mortalities and capture in gin traps. Although accidental
poisoning has previously been viewed as a threat, a review of the available literature
suggests that this is not the case and that these views stemmed from two isolated
incidents of captive animals. Electrocutions probably pose the greatest threat to
ground pangolins, with mortality rates of one pangolin per 11 km of electrified fence
per year recorded during this study.
Home range sizes of this arid-zone population are comparable to the home range
sizes recorded in mesic populations. Study animals in the Kalahari had Minimum
Convex Polygon (MCP) home range values of 10.0 ± 8.9 km² SD for adults and 7.1 ±
1.1 km² SD for juveniles, in comparison to the 0.17 – 23.38 km² MCP in Zimbabwe
and 1.3 – 7.9 km2 MCP in mesic north-eastern South Africa. These results are
surprising as arid-zone animals usually have larger home ranges than do their mesic
counterparts. It is hypothesised that this discrepancy is due to the fact that ground
pangolins in the Kalahari are on average 25 – 30 % smaller than their mesic
counterparts. This smaller body size means that individuals require a smaller home
range to meet their dietary requirements, which could be counteracting the trend of
arid-zone individuals requiring larger home ranges.
This research also found ground pangolins to be more active during the day in winter
and nearly entirely nocturnal during summer. These changes in photoperiodicity are
likely driven by adaptations to the extreme climatic conditions present at the study
site rather than predation pressure or changes in food resources, although the latter
may be playing a role as well. By being diurnal in winter, individuals avoid the
extremely cold night-time temperatures, thus saving energy that would otherwise be
spent on maintaining their body temperature. By contrast, becoming nocturnal in
summer allows them to avoid the extreme daytime temperatures, thus conserving
water.
The results of this study reiterate previous findings that ground pangolins are entirely
myrmecophagous and highly selective of the species that they eat. Study animals
were recorded feeding on only four ant and two termite species, representing 7.5 %
and 50 % of the total species richness of each of these families. This is similar to
previous research in mesic savannahs where five ant one termite species constituted
97 % of the ground pangolin’s diet. No seasonal differences in prey selection were
observed, although the species consumed did depend on the habitats that were
available to individual ground pangolins.
This study is the first to investigate the core body temperature (Tb) of a free-ranging
pangolin. These data indicated that Tb fluctuated cyclically between 32 – 35 °C and
reflected the activity periods of the animal, peaking when the animal was active.
When the individual was inactive, Tb steadily decreased, suggesting that it used daily
heterothermy to cope with the low food availability in this unpredictable environment.
In summary, ecological parameters between arid and mesic ground pangolin
populations are similar in some respects, but divergent in others. Arid-zone
populations are smaller overall and show a higher degree of diurnal activity. Despite
this smaller body size, home range values appear to be similar between arid and
mesic populations. Although the prey species eaten by ground pangolins in the
Kalahari differ from prey species in eastern South Africa and Zimbabwe, they
belonged to the same genera and were of similar morphology and ecology. The core
body temperature results confirm findings from previous captive studies that pangolin
body temperatures are lower than those of other eutherian mammals of a similar size. Furthermore, these data indicate that core body temperature is a lot more
variable than previously believed, and thus warrants further study. Overall ground
pangolin densities in the Kalahari appear to be double those in eastern South Africa
and Zimbabwe, although it is unclear whether this is genuine or whether it is an
artefact of individuals being easier to locate in the Kalahari. This study also confirmed
that electrocutions are probably the greatest threat to this species, and new threats
such as accidental capture in gin traps and road mortalities have also come to light. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Zoology and Entomology / unrestricted
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:up/oai:repository.up.ac.za:2263/36779 |
| Date | January 2013 |
| Creators | Pietersen, Darren William |
| Contributors | McKechnie, Andrew E., pietersen.darren@gmail.com, Jansen, R. |
| Publisher | University of Pretoria |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
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