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twaffle

Will reconnecting ecosystems allow long-distance mammal migrations to resume? A case study of a zebra Equus burchelli migration in Botswana

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The paper was distributed to those on the 'Save the Elephants' mailing list if anyone is interested, but I don't have the link as it was published in the Oryx journal. If you want any further information send me a PM.

 

Abstract Terrestrial wildlife migrations, once common, are now rare because of ecosystem fragmentation and uncontrolled hunting. Botswana historically contained migratory populations of many species but habitat fragmentation, especially by fences, has decreased the number and size of many of these populations. During a study investigating herbivore movement patterns in north-west Botswana we recorded a long-distance zebra Equus burchelli antiquorum migration between the Okavango Delta and Makgadikgadi grasslands, a round-trip distance of 588 km; 55% of 11 animals collared in the south-eastern peripheral delta made this journey. This was unexpected as, between 1968 and 2004, the migration could not have followed its present course because of the bisection of the route by a veterinary cordon fence. As little evidence exists to suggest that large scale movements by medium-sized herbivores can be restored, it is of significant interest that this migration was established to the present highly directed route within 4 years of the fence being removed. The success of wildlife corridors, currently being advocated as the best way to reestablish ecosystem connectivity, relies on animals utilizing novel areas by moving between the connected areas. Our findings suggest that medium-sized herbivores may be able to re-establish migrations relatively quickly once physical barriers have been removed and that the success of future system linkages could be increased by utilizing past migratory routes.

 

Whilst I've never been to Botswana, the ramifications of this paper are quite wide given the work being done between differing Parks and conservation areas to open up migration routes which, in many cases, have been considered long dead.

 

 

While the factors controlling migration in ungulates are not well understood, studies on insects and birds suggest that genetic, social and environmental factors are important, with species-specific differences in the importance of each factor (Schu¨z, 1949; Berthold et al., 1990; Olsen, 2001a,b; Chernetsov et al., 2004). Our results suggest that there may also be some genetic component of migration by ungulates. With a life expectancy of 15 years (Smuts, 1975), none of the zebra we recorded undertaking this migratory route could have learnt it from parental harems while juveniles. However, the stimulus to migrate must have been maintained, such that they resumed their migration once the fence was removed. The route taken could be because of innate directional cues, or perhaps by undertaking exploratory movements, following tracks of species such as elephants that also move great distances. While migratory birds such as whooping cranes Grus americana, which rely on strong social stimuli, only restart migratory behaviour after being re-taught the migratory route (Olsen, 2001a,B ), terrestrial mammals may be better able to re-establish migratory

behaviour because of the shorter distances travelled and the greater importance of environmental cues.

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Thanks, Twaffle, for posting this. I received it on the 'Save the Elephants' feed this morning but have not had time to read the whole thing yet. The excerpts you post reinforce the importance of opening/maintaining corridors between increasingly isolated island populations of wildlife. Existing corridors, both in Africa and elsewhere in the world, have very quickly demonstrated remarkable success, and in my opinion, are in many cases the only hope in the long term for species survival and a healthy, diverse gene pool. I would like to see Kenya creating more corridors, although it has started and certainly the elephant corridor between Mt Kenya and Lewa Downs is working a treat (except when the elephants get poached once they are through the corridor, as I am sure you know was the case recently with 4 out of the 7 elephants 'Save the Elephants' had tracked going through the underground pass.)

 

The more human encroachment squeezes traditional wildlife dispersal areas, the more important corridors will become.

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I agree with you totally Tanya. Yes, I had heard the dreadful news about the elephants. Sometimes it makes you want to yell and scream a lot with the frustration and stupidity of it all. :angry:

 

I have always asked about migration corridors whenever I've had the rare chance to talk to anyone with any influence. What I found really interesting about this paper was the ability for ungulates to resume their old migratory paths generations later. That has to give us hope for the future.

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I put up that news story a while back, and my concern was with the underpass: at present there is the webcam, but what happens if poachers target the underpass as an elephant bottle neck. Such a tunnel needs 27/7 monitoring, whether it be people on the ground, or webcams etc. Because such a thing has the possibility of becoming a real poachers paradise, especially in times of heavy use.

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You are right, Matthew - all these things have their down-sides. Monitoring the corridors will indeed become increasingly important, especially once the poachers latch onto the fact that they have a neat target there. By the same token, poachers - generally speaking - don't like to attract undue attention to themselves and they would certainly be rather obvious in and around these clearly defined corridors. In any event, without the corridors, the island populations are doomed, so all things considered IMHO it's still better to have the corridors than not.

 

As you say, Twaffle, it's amazing (and encouraging) how the ungulates have retained some instinctive/inbuilt knowledge/memory of their migration routes. It's not just elephants that are clever old sticks! :)

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Posted (edited)

I, for one, have never doubted the value of wildlife corridors, enhanced passage routes, etc. The concept of fencing as protection is, to me, pretty much a last resort. I certainly agree that a passage bottleneck increases the opportunities for poaching; however, I'll take that over no passage route anytime. I'm all for wildlife underpasses, overpasses, whatever.

Edited by Pangolin

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Pangolin - I agree the idea of fencing is anathema, especially in areas where the wildlife is migratory...but sadly, the way that the human population is increasing and encroaching on traditional wildlife lands, I think it may end up being the only option in many areas - to keep the humans away from the animals, and the animals away from the humans. :( But all the more reason for the corridors, as you say...without them, fenced island populations are doomed.

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