Kermit 's recent aggression means the green iguana is ready to mate

10/30/2007 12:00 AM

10/30/2007 8:52 AM

Kermit used to be a wonderful companion, say Karen and Zach, but has become somewhat of a beast.

They've been taking care of Kermit since he was a newborn and have watched the green iguana grow to 5 feet; he weighs 8 pounds. Kermit is housed in a huge enclosure but often is allowed to roam to a favorite spot near a window.

Unfortunately, for a reason unknown to Zach or Karen, Kermit has turned from a docile, gentle-spirited lizard into an aggressive monster. He used to enjoy being handled and carried on Zach's shoulder, but now neither Karen nor Zach can get near him without Kermit at the very least whipping his tail at them. He has bitten both of them, and at his current size and strength, those are painful bites. As much as it hurts Zach and Karen, they are at a point where they fear Kermit and are considering giving him up.

Iguanas can be good companions. This relationship may not be the same as one with a dog, or a cat, but nonetheless, there are definite bonds. Unfortunately, these bonds can be ruined when aggression rears its head. I suspect this would be the case with any companion, especially if the aggressive behavior is new.

Aggression can be inherent, acquired or hormonally driven. I do not think Kermit has inherent aggression; he used to be so docile and sweet. This leaves acquired aggression and hormonal aggression.

Hormonal aggression is an acquired behavior, but it has a specific physiological underlying cause. It is this cause that I believe has turned Kermit into a tyrannosaurus.

Male iguanas, like male members of many species, produce a hormone called testosterone once they begin to reach sexual maturity. This testosterone has several functions that have to do with mating, and in the case of iguanas, part of this behavior can be aggression. This aggression is manifested when a male is seeking a female for mating but encounters another male in the same pursuit. A ritual battle ensues and one iguana will dominate the other, allowing for the winner to mate with the female. In Kermit's case, there is no female iguana but there is still the testosterone and the resulting aggression.

Treatment is simply eliminating testosterone, which is produced in the testicles, from the bloodstream.

This procedure for removing the testicles is intricate because of the location of the testicles in iguanas. They're inside the body cavity and are closely associated with lots of important blood vessels that must not be disturbed. But the surgery can eliminate the likely cause of Kermit's aggression and restore his place as a cherished companion.

Jeff Kahler is a veterinarian in Modesto. Submit questions to Your Pet in care of LifeStyles, The Modesto Bee, P.O. Box 5256, Modesto 95352.

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