Drudgery and Dragons – Is “Housework” Fatal to Female Komodos?

Close up with a Komodo dragon (Image: Kenneth Garrett)

An international team of researchers has found that female Komodo dragons are living half as long as males do. The reason? “Housework.”

That’s right. Housework: The physically demanding tasks of building large nests, maintaining them, and guarding their eggs are shortening the lives of female Komodo dragons.

Members of the research team come from Australia, Indonesia, and Italy, and scientists are hoping that these findings will help plan conservation efforts for these endangered lizards’ by shedding light on their growth rate, lifestyle, and population differences.

Desperate Housedragons

The world’s largest lizard, the Komodo dragon is native to Indonesia’s Lesser Sunda Islands. They can grow up to 10 feet (about 3 meters) long and weigh more than 300 pounds (about 136 kg). The dominant predators in their habitat, their size and lethal bite lets them eat almost anything—pigs, water buffalo, smaller dragons, and even humans. (See related story: Komodo Dragons Kill With Venom, Researchers Find.)

Keep out: A female Komodo dragon guards her nest. (Image: Tim Jessop)

The study’s surprising findings indicate that males live to around 60 years old, while females only live an average of 32 years.  Males also grow significantly larger than females: Males, on average, grow 5 feet 3 inches (160 cm) in snout-vent length (not including tails) and weigh roughly 143 pounds (65 kg) at adulthood.  Females are smaller—only 3 feet 11 inches (120 cm) in snout-vent length, and about 48 pounds (22 kg).

Study co-author, Dr. Tim Jessop from the Department of Zoology at the University of Melbournesays, “The sex-based difference in size appears to be linked to the enormous amounts of energy females invest in producing eggs, building and guarding their nests. The process can take up to six months during which they essentially fast, losing a lot of weight and body condition.

“Males and females start off at the same size until they reach sexual maturity at around seven years of age. From then on females grow slower, shorter and die younger.”

The team studied 400 Komodo dragons for 10 years in Eastern Indonesia and have published their results, including a model of the dragon’s growth rate, in the current issue of PLOS ONE.

Live Fast, Die Young

This insight into the Komodo dragons’ growth rate reveals much about how the species prioritizes its energy use and reproductive strategies. The results suggest that males must spend their energy getting larger to reproduce successfully while females must spend their energy as part of reproduction, which results in their smaller size.

Komodo dragon eggs (Image: Tim Jessop)

Dr. Jessop says, “These results may seem odd to humans when the life span between Australian men and women differ by five years. But each species has different strategies to pass on their genes. For example humans invest a lot of energy in few children as raising them is very energy intensive, whereas insects will have hundreds of offspring with no input into their rearing.”

Understanding these behaviors could have important consequences for conservation efforts. Early female dragon deaths may be making competition for remaining females much fiercer among the males. The research team is hopeful that this clearer understanding of Komodo dragon growth and reproduction can aid in efforts to protect the endangered species.

Changing Planet

Focusing on content that entertains, astounds, and informs, Amy Briggs is freelance writer and former senior editor with National Geographic Books . The author of National Geographic Angry Birds Space, Briggs worked closely with National Geographic NewsWatch's David Braun on National Geographic Tales of the Weird. Excited by all things trivial, odd, and just unusual, she lives in Virginia with her family.