Wrestling with Crocs
An Interview with Dr. Alison Leslie
What's it like to capture an 18-foot Nile crocodile for research
purposes? To touch its skin, smell its breath, hear its growl? How do
you weigh a half-ton croc? Are you willing to do what it takes to find
nests, determine its sex or pump out its stomach contents for study?
Most important, how do you release it and keep all your body parts at
the same time? Dr. Alison Leslie, a crocodile researcher at the University of Stellenbosch in South
Africa, describes the often hair-raising aspects of studying the ecology
and behavior of Nile crocodiles in South Africa's Lake St. Lucia.
NOVA: What would happen if you fell overboard amid a group of wild Nile
Leslie: It's definitely not something I'd want to happen to me. If it
was winter and the water was cool and they weren't that hungry, you
might be able to get away with a few scratches and bruises and perhaps
the odd lost limb or two. But if it was a hot day and they were in a
feeding frenzy, I don't think you'd have two seconds to remember your
NOVA: Did you ever have any close calls?
Leslie: If I'd had a really close one I probably wouldn't be here right
now. We got bitten a few times by the smaller crocs, those about one and
a half meters (five feet). They can give you a pretty bad nip. Once a
huge male charged our little aluminum boat. It was breeding season and we had obviously entered his
turf. Luckily the driver was wide awake. He spun the boat around, and we
took off. Most of the close calls were with hippos, actually.
NOVA: They're more dangerous?
Leslie: They're the number one animal killer, if you rule out the
mosquito. Hippos come out of the water at night to graze, but, of
course, they don't spend the entire night out of the water. We used to
drive right over them, because you just don't see them. Often in the
middle of the night you'll see those beady red eyes and prepare to noose
what you think is a croc, and it turns out it's a little baby hippo
parking next to mom, who you didn't see.
NOVA: I've heard that many attacks on people occur while crocs are
defending their nests, yet you do your nesting surveys on foot. Isn't
Leslie: It's pretty hair-raising at times, because to find the nest site
you have to walk between the lake edge and the crocodile nest. Now, croc mothers defend their nests
unbelievably well. But six or eight people, as we usually have when we
do these counts, is too much for them, and they bolt for the water,
because that's where they feel safest. You'll be walking along, making
noise to scare them off the nest, but sometimes they don't hear you, and
suddenly one will run right in front of you to get to the water's edge.
You'll look up, and it'll be coming straight for you. You're carrying
backpacks and tents and all sorts of equipment. You either run forwards
or backwards as best you can, or you just jump. And they shoot on past
NOVA: They don't stop to bite you?
Leslie: I think that's the last thing on their minds. Because once they
leave their nests they realize that you know that they're kind of
vulnerable. All they want to do is get to the water. Sometimes, however,
after the mother's left, you'll be standing on the nest taking
suddenly she'll come back. You have to remember that crocs can outrun
you quite easily. For short bursts, they can run 35 kilometers an hour
(18 mph), which is about what an Olympic athlete can do. And they can
come out of the water even faster. If they've had time to build up
speed, they can shoot themselves out of the water at 70 kilometers an
hour (43 mph). It can be pretty terrifying at times.