NILE CROCODILE: T.S.D. II/Alien Plant

This month, the Nile crocodile’s of the St. Lucia Estuary in South Africa are hatching, and if the temperature’s been right, there just might be some males among the crocodile babies. I’m Jim Metzner, and this is the Pulse of the Planet, presented by the American Museum of Natural History.

Right now, we’re listening to the sounds of newly hatched baby crocodiles.

Many reptiles exhibit a phenomenon called temperature dependent sex determination, which basically means that the temperature at which the eggs were incubated determines the sex of the young. St. Lucia’s Nile Crocodiles have a small window, roughly five degrees Fahrenheit, in which males are born. If the temperature is any colder than 89 degrees or warmer than 94 degrees, and the crocodile is female.

Telling us more is physiological ecologist Alison Leslie:

“This area represents the southernmost extent of the breeding range for Nile Crocodiles on the African continent. In other words, at this particular temperature of incubation, it will be a little difficult for those eggs to actually produce males because the males require the higher temperatures. So Saint Lucia is on the edge of the male producing temperatures.”

Dr. Leslie explains that the introduction of a fast-growing, non-native plant species to this region has created a related, additional obstacle to the birth of male crocodiles.

“When you get something like an alien plant coming along that’s causing a shading effect on these actual nesting sites, you’re reducing the temperature. So instead of certain areas producing a certain percentage of male hatchlings, they’re producing a hundred percent or at least the majority female hatchlings. And this is obviously going to lead to long term eventual extinction of the species in that area.”

We’ll hear more about crocodiles in future programs. Pulse of the Planet is presented by the American Museum of Natural History. I’m Jim Metzner.

NILE CROCODILE: T.S.D. II/Alien Plant

The statistical rarity of the birth of male Nile Crocodiles is leading toward the eventual extinction of the species.
Air Date:02/04/1998
Scientist:
Transcript:

This month, the Nile crocodile's of the St. Lucia Estuary in South Africa are hatching, and if the temperature's been right, there just might be some males among the crocodile babies. I'm Jim Metzner, and this is the Pulse of the Planet, presented by the American Museum of Natural History.

Right now, we're listening to the sounds of newly hatched baby crocodiles.

Many reptiles exhibit a phenomenon called temperature dependent sex determination, which basically means that the temperature at which the eggs were incubated determines the sex of the young. St. Lucia's Nile Crocodiles have a small window, roughly five degrees Fahrenheit, in which males are born. If the temperature is any colder than 89 degrees or warmer than 94 degrees, and the crocodile is female.

Telling us more is physiological ecologist Alison Leslie:

"This area represents the southernmost extent of the breeding range for Nile Crocodiles on the African continent. In other words, at this particular temperature of incubation, it will be a little difficult for those eggs to actually produce males because the males require the higher temperatures. So Saint Lucia is on the edge of the male producing temperatures."

Dr. Leslie explains that the introduction of a fast-growing, non-native plant species to this region has created a related, additional obstacle to the birth of male crocodiles.

"When you get something like an alien plant coming along that's causing a shading effect on these actual nesting sites, you're reducing the temperature. So instead of certain areas producing a certain percentage of male hatchlings, they're producing a hundred percent or at least the majority female hatchlings. And this is obviously going to lead to long term eventual extinction of the species in that area."

We'll hear more about crocodiles in future programs. Pulse of the Planet is presented by the American Museum of Natural History. I'm Jim Metzner.