Saturday, June 9, 2012

Lion dummies

A lot of folks have inquired lately about what’s going on over here, perhaps because there have been so few contributions to this blog lately. In fact, we’ve been extremely busy doing loads of different things here, but this week in particular has been exciting because we’ve been doing pilot experiments looking at hyena responses to life-sized stuffed lions. The stuffed lions are on loan to us from Craig Packer’s lab; one of his graduate students working on inter-specific relationships among large carnivores, Ali Swanson, brought them up to us from Serengeti a few days ago. These lions had been used several years ago when Packer and colleagues were inquiring why lions have manes, but encounters between the fake and real lions in those experiments caused the stuffed lions to suffer some wounds. Therefore, upon Ali’s arrival at fisicamp, our first task was to repair some of the damage inflicted on the stuffed lions by their real counterparts. Although Ali and I initiated the repair work, both Josephs and the other guys who work in our camp soon took over patching various holes in the stuffed lions. Stephanie Dloniak flew down to the Mara with her sound equipment so we could call hyenas in to interact with the stuffed lions.

My goals in asking Craig & Ali if we might borrow the stuffed lions was to run some pilot experiments inquiring about the circumstances under which hyenas help one another. One of the most common forms of cooperative behavior among hyenas is the formation of coalitionary mobs to drive lions away from their kills or from  the hyenas’ own dens. With the life-size models, I hoped to vary odds ratios (numbers of hyenas relative to numbers of fake lions present) and pay-off schedules (the quantity of meat available for the hyenas to steal from the fake lions) to inquire how these variables affected the hyenas’ tendencies to call in allies and cooperate with one another. Going into this, we had no idea whether the hyenas would even behave towards the fake lions as though they were real, but they most certainly DID for a surprisingly long time!

It rained hard the night Ali and Steph arrived in camp, so the next morning we ran an initial pilot experiment with the Talek East clan, whose home range includes our camp, so we didn’t need to drive far in the mud to set it up. We made both models into females by removing the mane from one model, placed the stuffed lions on the side of a hill, and dumped a few chunks of meat in front of the models. Then Steph played loud sounds for several minutes of lions and hyenas interacting over a kill through a speaker mounted on the roof of one car (the sound tape was made in Botswana by former fisicamper Anne Engh; thanks Anne!).  We had observers and videographers in each of three vehicles positioned at 12, 9 and 3 o’clock, such that they would be able to capture events and hyena IDs from multiple angles. We performed this experiment at the edge of the Talk East home range, so the call-in tape only attracted 5 hyenas, but they appeared to be fooled by the fake lions, as they were clearly very nervous. Some of the observers were situated on car roofs or standing to film out of open roof hatches in our vehicles, and the hyenas in this clan are very shy, so they all ended up running away after several minutes rather than attempting to get the meat chunks. We failed to attract any adult females to that scene (only adult males and subadults), which might explain why none of the arriving hyenas vocalized to call in allies. But we learned valuable lessons from that little experiment nonetheless including how our vehicles needed to be positioned relative to the fake lions, and that we all needed to remain strictly inside our cars.

Yesterday morning we ran the experiment on No-Name Hill, which is in the center of the Talek West territory, not far from the communal den. This time, we kept all the vehicles fanned out at much tighter angles to one another so the hyenas had more unobstructed space in which to move around the fake lions, and all observers and videographers remained inside their cars. We also made one of the two lions into a male by replacing its mane with velcro, positioned the fake lions at the edge of a small clump of bushes, and increased the number of meat chunks placed under the chins of the fake lions. Once again, Steph played the call-in tape for a few minutes, and almost instantly hyenas started appearing in the tall grass of the surrounding plains.

The first hyena to arrive on the scene was an adult female who ran around whooping madly while also pooping in apparent fear of the fake lions. Shortly thereafter more hyenas arrived, and soon we had nearly thirty clan-members loping excitedly around the fake lions, and vocalizing. We heard alarm rumbles, and various hyenas whooped and greeted at the scene, so they were clearly “talking” to one another. Soon we had nearly 30 hyenas there. Most hyenas kept a respectful distance from the lions, but they were clearly all scenting the meat. Some hyenas would periodically start to move in closer to the models but then one would scare itself, and everyone would dash away again. You can see the hyenas’ fearful behavior in many of the great photos Steph took (a few shown here).

I found it very interesting to watch individual variation in boldness toward the models, indicated by how close the hyenas were willing to approach them.  Some approached to only a single body length away whereas others stayed 100 body lengths from the lion models. Eventually, when the models did nothing for quite a long time, some of the boldest females, including Loki, Parcheesi and Monopoly, darted in and grabbed chunks of meat from under the lions’ noses. They were then chased all over the place by higher-ranking hyenas until they eventually dropped their chunks. Even after all the meat chunks had been taken, lots of hyenas were still milling about, so we had to pull our cars forward and block the hyenas’ view while we loaded the fake lions back into our pick-up and covered them up.

Disappointingly, we did not see even a single coalition form during the entire experiment. This may be because the lions never did anything to keep the hyenas from eventually coming close enough to grab the meat. We were hoping to try another experiment this morning with the Fig Tree Clan, but there happened to be real lions prowling about at the call-in site when we arrived, so we will try that again tomorrow if the actual lions are gone. This time we hope to use hidden speakers to periodically play lion sounds from under the models to determine whether this might affect the hyenas’ tendencies to cooperate. But even if they still fail to cooperate, these lion models could clearly still be very useful in analyses of boldness and communication among the hyenas. And as everyone present will tell you, these experiments are a LOT of fun!

Thanks again to Steph Dloniak for taking all these wonderful photos!


dee said...

Thanks for posting, it has been a long dry spell,l blog wise, and it's good to get news, especially such interesting stuff.

Anne said...

Fun, fun, fun! Wish I was there to join you guys! Kay, I do have some just lion recordings (roars). I can't remember if I sent them to Steph or not. They are great, close, clean recordings. If you are interested, I can try to get a copy to you. I think that I only gave Steph the best few minutes of that lion-hyena recording. If you want more, I have more of that , too, though as I recall the original has lots of insect noise (I filtered it out for the part you guys are using).

Tor Bertin said...
This comment has been removed by the author.
Tor Bertin said...

Out of curiosity, how much research has been performed on the dynamics of food acquisition in these kinds of encounters? On the one hand, bold individuals may stand a higher chance of grabbing some meat, but they would also consequently have a greater risk of being attacked by lions, assuming the lions are still near the carcass. And, as you mentioned, less bold hyenas may be more likely to steal scraps from more bold hyenas given that the risk of injury is likely lessened from a conspecific than from a lion if the lion isn't actively engaged in combat with other hyenas.

Are these individual behavioral variations in any way related to social structure, or is the behavioral plasticity not particularly constrained by things like matrilines?

Mostly thinking 'out loud' here, but it's some food for thought.

David said...

Using stuffed lions would surely effect the approach and behaviour of the hyenas. No smells and no movement coming from these stuffed lions would have left the hyenas somewhat baffled, and would naturally be more apprehensive of animals displaying odd behaviour that they're not accustomed to.

Like Tor Bertin, I'm just thinking out loud.

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