Pangolin Survival Strategies in Dry-land Savannahs: a Pilot Study in Namibia
Bruno Nebe & Paul Rankin
Jan 2012: Recovery of Okulunu's GSM/GPS combo
Because of other commitments and the heavy rains which ensued at Mundulea, it was to be almost two months after Okulunu's release on Nov. 7th 2011 before there was a chance to recover the combination tracking device, long after its battery would have died. With a better idea now of the pangolin's home range Bruno and Tim could focus their search using the Yagi receiver to pick up signals from the animal's RF tag at about 10pm on Jan 3rd 2012 and find Okukunu in dense bush at about 1:30am within a few km of its previous release point. Whilst tracking it down following more accessible fence lines and roads, the RF signal would disappear and reappear, presumably as the pangolin walked around obstructions. With no wind, it was finally possible to sit and quietly observe the pangolin with a red light from as close as 2 metres without disturbing it. The pangolin was busy foraging, digging for about two minutes to get ants, then stopping to feed. Okulunu was then recaptured and samples of the aggressive biting ants it was eating taken for later identification.
RF tracker and combo. device
removing combo. device
(photos taken by Bruno Nebe. Click on any photo is this blog to enlarge it)
Very interestingly after recapturing Okulunu that night, a fresh feeding site was noticed after a noise nearby from another pangolin which must have been foraging nearby only minutes earlier, perhaps being disturbed by the noise of two trackers! For the first time ever, its footprints could be clearly seen. Unfortunately, with fading torches at 2:30am, the other pangolin could not be followed into the bush. However, the discovery indicates either that the home territories of these two pangolins definitely do overlap, or that the other pangolin was young and on the move as it had not yet established its own home territory.
In the only published longitudinal study of established Cape Pangolins' home ranges in Sengwa, Zimbabwe, hardly any territorial overlap had been found between pangolins of the same sex, only occasionally an overlap of a male's and a female's territories, viz:
Martha E.. Heath and The Late Ian M. Coulson, 'Home range size and distribution in a wild population of Cape pangolins, Manis temminckii, in north-west Zimbabwe', Afr. J. Ecol. 1997, Volume 35, pages 94–109. They observed that: 'smaller (younger) individual Cape pangolin have smaller home ranges than the larger adults'..'the spatial relationships between the home ranges of neighbouring pangolins indicates that within sexes the amount of true overlap is quite small (1·72% for females, and 0·07% in males). Considerably greater overlap was observed between sexes, all of which could be accounted for by males that moved into the home range of a female for a limited period of time'...'we believe this overlap is associated with mating.'
Whether same-sex pangolin home territories do in fact overlap more frequently, e.g.where food sources are in good supply, or whether the other pangolin was of the opposite sex to Okulunu, ie female we would love to know. Having a better knowledge of the size of the Cape Pangolin's home territory and range as a function of age/weight, gender and food supply is key to conservation work.
Scale used for combo attachment
large ticks found on Okulunu
(photos by B. Nebe)
Back at the farmhouse, the GPS/GSM combination tracking device was removed. Although rather bulky and not streamlined, the device appeared undamaged by 2 months of attachment, while the scale carrying the device was not abraded or harmed. Okulunu's weight was still 13kg as before. The animal had quite a bad infestation of very large ticks, possibly from having spent time in a cattle-raising area in its territory. Next time the animal is recovered for changing its RF tag (the RF transmitter has an 18 month battery life and was working well, although further wear to the aerials' roots was noticed), we can try to help rid it of the tick problem. The animal was re-released on Jan 4th 2012 close to the last capture site.
Traces of rust on aerial (Photo by P. Rankin)
The combination tracking box was returned to Paul in the UK for investigation. On opening the box, some rust was visible on one of the internal aerial plates, but a lifetest after recharging its battery showed that all the electronics still function as expected, giving about 10 days lifetime with both its GSM location-interrogation and GPS logging units performing correctly. We believe that moisture must have entered the box despite the silicon grease sealant during the very heavy rain which fell in Mundulea at the time the unit stopped functioning.This caused a non-catastrophic short-circuit drain from the battery. Although only a few days' worth of GPS data sampled every 2 minutes was captured before the battery died, this logs the times it was underground in a den, Okulunu's movements and its foraging behaviour with dwell times at successive feeding locations before moving on. The GPS track, together with the coordinates at which Okulunu has been found previously allow us to start mapping out its home territory - see the map below showing the waypoints (red flags) and logged 2-3 days movement (red track). Next time of course, a better moisture-tight enclosure will be employed and a more streamlined casement with a larger battery capacity would be desirable, but we feel that this prototype device has successfully proved the principle of using a GPS/GSM combination tracker with pangolins.
Waypoints of Okulunu's sightings, some location interogations via cell phone, plus capture & release points shown as red flags, as well as 2-3 days of its GPS log (red track)
Subsequently during February-April 2012, Namibia and Mundulea has experienced extremely unusual rainfall, more than any since 1932. This has made the whole Northern part of the property inaccessible, with floods extending many kilometres outside Mundulea. Probably Okulunu has been driven for the first time in its guessed 40-50years of life some 10-20km away to find dry land and food. We hope that after a few months once the floods subside, this mature pangolin will return to its well-established home territory so that we can find it again, provided the RF tag works, and continue to study it.