Wouter van Hoven

Adaptation of ruminants to browse and grass diets: are anatomical-based browser-grazer interpretations valid?

As a result of pioneering work of Hofmann (1973, 1989), nutritional ecologists classify ruminants into three feeding-type categories: browsers (“concentrate” feeders), grazers, and intermediate or mixed feeders. Hofmann proposed that these feeding types result from evolutionary adaptations in the anatomy of the digestive system and that one consequence is shorter retention of the digesta in the rumen of browsers, and thus a decreased efficiency of fiber digestion relative to that of grazers. We examined the hypotheses that (1) fiber digestion of browsers is lower than that of grazers, (2) salivary gland size is larger in all browsers than in grazers, (3) the browsers larger salivary glands produce larger volumes of thin serous saliva than those of grazers, and (4) thus, browsers have higher liquid passage rates than do grazers. We found that the extent of fiber digestion is not significantly different between browsers and grazers, although fiber digestion is positively related to herbivore size. In general, salivary gland size is approximately 4 times larger in browsers than grazers, but some browsers (e.g., greater kudu) have small, grazer-sized salivary glands. Resting (non-feeding or ruminating) saliva flow rates of mule deer (browser) and domestic sheep and cattle (grazers) were not significantly different from each other. Finally, ruminal liquid flow rates were not different between feeding types. We conclude that many of Hofmanns nutritional and physiological interpretations of anatomical differences amongst ruminants are not supportable.

Survival rates and causes of mortality of leopards Panthera pardus in southern Africa

The International Foundation of Science (D/4984-1), Wild Foundation (2008-011), Wilson Foundation and the University of Pretoria. LHS was further supported by the National Research Foundation (74819), FD by the National Research Foundation and a research fellowship from the University of Pretoria, and MJS by the Department of Science and Technology Centre of Excellence for Invasion Biology and the National Research Foundation.

Factors Affecting Location Failure of GPS Collars Fitted to African Leopards (Panthera pardus)

Recent technological advances in Global Positioning system (GPS) technology have generated an Increase in the use of GPS collars fitted to wild animals to track their movements. GPS units are advantageous compared to other methods of remote tracking of animals in that the have the ability to gather large quantities of spatial data that may be accessed remotely. However, animal behaviour, topography, vegetation, and seasonality could all influence GPS acquisition success and therefore bias results from GPS technology. Here we analyse temporal and seasonal patterns associated with GPS acquisition failures in five GPS collars fitted to leopards (Panthera pardus) in the Waterberg region of South Africa. Of 6565 attempted GPS acquisitions, 19% (1236) failed with the location failure rate of Individual collars ranging from 15–29%. Single failed attempts accounted for the majority of location failures, suggesting that failure was caused by temporary blockage to satellites. Failure rates were significantly higher during the day and there were Indications that they were higher during the wet season than in the dry season. Failures were also clustered in space for some Individual animals. Our results suggest that temporal patterns of animal behaviour and habitat choice Influence the probability of GPS location failures in this species. We therefore suggest that potential biases should be accounted for when using GPS data to analyse movement and habitat selection in this and similar carnivore species.

The Relative Importance of Trophy Harvest and Retaliatory Killing of Large Carnivores: South African Leopards as a Case Study

There are considerable challenges in the conservation of large carnivores, caused by large area requirements, low reproduction rates and low population densities coupled with their tendency to cause conflict with humans. Trophy hunting is one strategy to increase support for large carnivore conservation. Leopards, Panthera pardus, rank among the most sought-after trophies in South Africa. However, trophy hunting has been suggested as partly responsible for leopard population declines, and leopards are also killed in retaliatory actions. In this study we used a stochastic population model to evaluate the relative influences of retaliatory killing and trophy harvest on leopard population persistence, and to assess the sustainability of the current leopard trophy harvest in South Africa. There was a stronger effect of variation in retaliatory killing than of harvest on population persistence. Although we found low extinction risks for South African leopards within 25 years, high risks of population declines across a wide range of simulation scenarios call for concern regarding the viability of the South African leopard population. We suggest that conflict mitigation may be more effective in promoting leopard persistence than restricting trophy harvest, and that accurate estimates of retaliatory killing are necessary for assessments of harvest sustainability.

Nile crocodile Crocodylus niloticus telemetry: observations on transmitter attachment and longevity

Abstract The aim of this study was to investigate transmitter attachment and longevity on Nile crocodiles (Crocodylus niloticus) in the Flag Boshielo Dam, Mpumalanga, South Africa. From August 2002, 15 adult Nile crocodiles were captured over a 19-month period in the Flag Boshielo Dam. Conventional VHF transmitters were fitted to the tails of eight male and five female Nile crocodiles, while a GPS/GSM transmitter was fitted dorsally to the neck of one male and one female Nile crocodile. There was no significant difference in the total lengths of male and female Nile crocodiles captured for transmitter fitment. Overall, 40% of the transmitters failed, while an equal number was broken off. Neither sex, nor total length of the Nile crocodiles predicted longevity of transmitters from time of fitment to time of failure or destruction and loss. In future, the tails of crocodiles should be avoided when attaching transmitters, as conspecifics seem to target this area during agonistic behaviour. Moreover, it is essential that transmitters and their attachment configurations be tested on the target species before a study commences. Lastly, we urge researchers to routinely provide information on the performance of transmitters and their fitment configurations.

Two new entodiniomorphid Triplumaria ciliates from the intestine of the wild African white rhinoceros

Two new species of Triplumaria in the order Entodiniomorphida, T. alluvia n. sp. and T. grypoclunis n. sp., are described from the large intestine of the wild African white rhinoceros. T. alluvia has three bud-shaped caudalia, one broad skeletal plate with a wavy left dorsal edge, and an axe-shaped tail flap. T. grypoclunis has three short arched caudalia, two broad skeletal plates, and a pointed and ventrally curved tail flap. These two new species have a C-shaped adoral polybrachykinety, a slender perivestibular polybrachykinety, and paralabial kineties in their retractable adoral ciliary zone. In T. alluvia, the perivestibular polybrachykinety is joined to both ends of the adoral polybrachykinety and paralabial kineties along the ventral side of the adoral polybrachykinety, showing the same arrangement as in Cycloposthium species. In T. grypoclunis, the perivestibular polybrachykinety is joined only to the right end of the adoral polybrachykinety and paralabial kineties along the left ventral side of the adoral polybrachykinety, showing an arrangement analogous to the Tripalmaria species.

Quantifying the Impact of Off-Road Driving on Root-Area Distribution in Soils

Studies on the effects of off-road driving on soils were conducted in the Makuleke Contractual Park of the Kruger National Park. The studies were conducted on three different soils with different textures and soil compactibilities. Traffic pressure was applied with a game drive vehicle loaded with 10 sand bags, each weighing 70 kg, plus the driver. This gave a total vehicle mass of 3795 kg, simulating a vehicle fully laden with tourists. The results of the study reported here included comparing of the effects of four different tyre pressures on the root area distribution below each tyre pressure. At all sites, root density fractions under the tracks were reduced significantly at all tyre pressures, compared with the control values. Results indicated that root penetration percentage and root area distribution were reduced drastically as tyre pressure increased. Our work reaffirms previous research showing that higher tyre pressures cause higher sub-soil compaction than lower tyre pressures. Thus, driving with lower tyre pressures when driving off-road should be considered when developing management strategies for off-road driving in wildlife protected areas.