Scientists try to keep Cuban crocodiles
from disappearing
By Scientific American, adapted by Newsela staff
12.14.14
The Cuban crocodile was already considered to be one of the world’s most endangered
crocodiles. Now it is at even greater risk of disappearing than scientists had previously
realized.
The problem is that the Cuban crocodile has been mating with its American cousin.
It seems the island’s native species has been doing quite a bit of interbreeding with the
more common American crocodile. Over time, its offspring are becoming less and less
"Cuban."
Gene Pool Is Not As Deep
Scientists consider the Cuban and the American crocodile to be separate species
because each has its own set of genes. Genes can be thought of as instructions that
are passed down from parent to child. They are unique. They shape how living things
look and behave. In humans, for example, there is a gene for red hair. In Cuban
crocodiles, there are genes that make them what they are. A species' complete set of
genes is known as a genome.
As Cuban crocodiles mate with American crocodiles, the Cuban crocodile genome is
becoming more mixed. In each baby, a portion of the Cuban crocodile genome is
replaced by American crocodile genes. With each new generation, more and more
Cuban genes are lost. Eventually, the species could disappear.
Scientists already knew the two species were mating with one another in the wild.
However, they only recently discovered just how frequently this was happening.
Wild Crocs Tell The Story
A team of researchers led by Yoamel Milián-García studied genes found in the scales of
227 wild crocodiles. They found that the level of interbreeding is much higher than
previously believed: 49 percent of the wild crocodiles sampled had mixed genes.
The Cuban crocodile was once found throughout the island of Cuba. However, overhunting starting in the mid-1800s caused its population to drop. Today there are only
about 4,000 Cuban crocodiles left.
Now the Cuban crocodile is at risk of losing what makes it distinct. Its genome may
become so "American" that it will not be a separate species anymore.
Scientists say the Cuban crocodile is special and worth protecting.
Milián-García is trying to determine what causes the interbreeding. He suspects that
hunting and the disappearance of swamps and marshes is driving both species into the
same areas. Once living side by side, the two types of crocodile are much more likely to
interbreed.
Captive Crocodiles Offer Hope
In addition to the wild crocodiles, Milián-García's team also studied 137 captive Cuban
crocodiles. The animals live at the Zapata Swamp Captive Breeding Farm. Since 1974,
Cuban crocodiles at the farm have been kept apart from American crocodiles. A study
of their genes gave scientists some reason for hope.
Around 30 percent still had certain Cuban crocodile genes that were not found in other
crocodiles. In the future, those animals could be used to help keep the Cuban crocodile
from disappearing.
Tomorrow’s Question is below:
Read the paragraph from the section "Wild Crocs Tell The Story."
Milián-García is trying to determine what causes the interbreeding. He suspects that
hunting and the disappearance of swamps and marshes is driving both species into the
same areas. Once living side by side, the two types of crocodile are much more likely to
interbreed.
This paragraph develops the central idea in the article by describing:
A
minor details
B
causes
C
important events
D
effects