Sept-Oct 2012: Results on Okulunu's Homing Instinct

Very little has been reported in the literature on the homing behaviour of pangolins released outside their home territory, other than in the paper:
M. E. Heath & I. M. Coulson, ‘Preliminary Studies on Relocation of Cape Pangolins’, S.Afr. J. Wildl.Res. 1997, 27(2), pp 51-56.
Here they reported that the pangolin 'p22' returned 5 km back to its home range. It is not clear whether the pangolin was familiar with the terrain between its release point and established home territory and so used its memory of landmarks (scent marks?) to return, or whether some other sense or navigation ability is available to the animal.

After the lucky recovery of Okulunu on 27th Sept. 2012, one of our GPS+GSM 'combo' devices (see earlier posts) was attached to the pangolin in addition to its RF tag. The pangolin was then released at a location across a ridge, close to, but outside its usual home territory. Its GPS locations were then logged by the device every 2 minutes for 7-10 days afterwards. Battery life was conserved by programming the GPS location logging to be turned off during the daytimes after the release day, and the GSM unit to be turned on to aid finding the animal only at specific times during the night. The whole recapture and release procedure was followed twice, uploading the stored GPS data and replacing the combo's batteries after the first run, finally locating the animal and removing the combo device subsequent to the second run to leave the animal unencumbered. Analysis of Okulunu's detailed, timed movements on the two runs subsequent to releases proved fascinating.  (Of course, we do not know whether the release location was familiar to Okulunu from previous wider explorations outside its preferred home territory.)

After the first release on Sept 27th, Okulunu spent 6.5 hrs on local movements (search/orientation?) before setting off in almost a straight line to cross the intervening ridge and head for its usual home territory. It continued on its initial bearing after crossing a fence and afterwards subsequently spending a day resting in a den en-route before returning to foraging in its home territory on subsequent days before recapture. An animated log of Okulunu's movements is viewable using the 'Map View' at:
http://www.a-trip.com/tracks/view/133484

Movements in first hours, Run #1

Movements in first days, Run #1

After the second release on Oct 4th at the same location, Okulunu spent this time longer, viz. 11.5 hours, exploring the release area before setting off homeward at a very similar time of night as on the first run. It crossed the ridge in a different direction than on the first release, but subsequently the fenceline at a similar place, this time after spending some daytime sleeping in a different den than on the first run. As before, the complete track is animated in the 'Map View' at http://www.a-trip.com/tracks/view/133496

Movements in first day, Run #2

Movements in first days, Run #2

A clear homing behaviour can be seen, reproduced in these two sets of results, which warrants further research on how the pangolin navigates.

The detailed GPS logs of these two pots-release runs reveal further information on the active foraging periods per night and its den locations which might be correlated with fauna, ant prey availability etc. It was interesting that on one night, Okulunu was active only for two hours- whether that was due to an abundance of food in the local area or a threat such as a honey badger is not known.

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