In the 1980's, a group of orphaned elephants was relocated to a national park in South Africa with the hopes of repopulating the area. But park managers didn't realize they were creating a juvenile delinquency problem. In the absence of older bulls, the young male elephants matured too soon and ended up killing endangered rhinos. Steve Curwood speaks with elephant researcher Rob Slotow on how the problem was solved.
CURWOOD: Two decades ago, officials in South Africa's Kruger National Park decided they had too many elephants, and thinned the herd by killing adults. Some of the young elephants orphaned in this cull were sent to another national preserve called Pilansberg. But in the mid-90s, park rangers there realized an unintended and grizzly consequence of the relocation: elephants began killing rhinos. Researchers say the relocated male elephants, now teenagers, had entered into abnormally early, and abnormally long, periods of musth. That's the bull elephant's state of heightened testosterone and aggression. Dr. Rob Slotow, a biologist with the University of Natal in Durban, was called in to help find a solution to the attacks. He says these elephants were exhibiting deviant behavior because their normal hormonal cycles were severely disrupted.
SLOTOW: In a normal society, a male elephant would gradually have extended periods of musth. And during this process of gradually acquiring musth, they get experience at dealing with having elevated testosterone coursing through their blood, having these aggressive fits, if you like. And they learn to deal with de-escalation of conflicts when they can't win. So these bulls, the young bulls in Pilansberg, don't have this experience of de-escalating when in musth, because they've never encountered a bull that's actually dominant to them. There are no older bulls around that can beat them in a fight. And so they don't know how to de-escalate when they chase off to these rhinos.
CURWOOD: Can you tell us why you think the rhinos were singled out by bull elephants for aggression?
SLOTOW: Well, in natural populations, elephants and rhino typically interact with each other. And this also typically takes place around water holes. Animals typically will signal to each other intent to fight. There will be posturing or moves towards each other. And very rarely do physical interactions take place. And in most instances, one of the two, either the rhino or the elephant, would move away from the victor, who remains behind. What we believe happens in the instances where elephants are killing rhinos is that the rhinos are de-escalating. They're deciding they can't win this fight. They turn away and they move away. And what we believe is abnormal is that the elephants actually chase the rhinos down, chase them at the run, and will then attack them with their tusks.
CURWOOD: So then, someone had the idea, I gather, to bring in some older males to regulate the hormones of these young bucks. What happened when that was done?
SLOTOW: Well, the older bulls were brought in, in February 1998. And after about six months or so, the population settled down to, what we describe as, a normal population structure, in terms of the social behavior. And also after about eight months or so, the first of the Kruger bulls came into musth, and the young resident Pilansberg bulls started showing shorter and shorter musth periods.
CURWOOD: And what happened to the rhino killing?
SLOTOW: These mortalities had ceased completely since the introduction of these adult elephants.
CURWOOD: Now, some could say that this is a cautionary tale about the unintended consequences of human intervention in the highly complex animal society. What would you say?
SLOTOW: Well, I think that's exactly the point. When people try new ideas, there are consequences of them that we may not know about until a number of years have passed. And this is particularly so when you talk about long-lived species, such as elephants. What's happened here is we've learned a lot about elephant behavior, and we've also learned a lot about the procedures that should be followed when major undertakings, such as this, are taken. Not only should one consider what the elephants eat, is their food present, etc., but also, what the sociological consequences would be for animals such as elephants. Although, you know, some rhino were killed, this elephant population has established itself. It's a good population. The elephants were saved from culls in Kruger National Park, which is a nice thing, as well. And they are part of the ecosystem. So, the principle of translocating them wasn't a wrong principle, but what we've learned from this is that we need to translocate, essentially, miniature populations, which have the correct structure. And this is what is taking place now. So, the main source of elephants, Kruger National Park, have learned from this and they do translocate now complete female herds with adult females, and are also now sending older bulls with these populations.
CURWOOD: These elephants were orphaned by park rangers, the ones that we're talking about. But what happens when there's poaching in which, in fact, the biggest males with the biggest tusks are the targets?
SLOTOW: I think this is the next area where we're going to learn about problems of elephant society. In areas further north in Africa, in East Africa, where there were major poaching events and most of the older animals would have been wiped out, we now have young populations that don't have the guidance of these older animals. One such example might be young males come into musth earlier, but there may be other sociological problems that these populations are going to face. There may be problems with the females, etc. And we're only really going to learn about these problems through close study of these populations.
CURWOOD: Dr. Rob Slotow is a biologist at the University of Natal in Durban, South Africa. His paper on bull elephants appeared in a recent issue of Nature. Thank you, sir.
SLOTOW: Thank you.
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