The high cost of reproductive inequality

Image of Indonesia's Komodo dragons from Scientific American.

Dr. Tim Jessop from the University of Melbourne, Australia and colleagues  spent eight years following 400 Komodo dragons (Varanus komodoensis) to learn more about their growth rate, lifespan as well as differences between populations on isolated Indonesian islands. Their most surprising finding was that female Komodo dragons only live an average of 32 years whereas males live for about 60 years. Females are additionally smaller (1.2 meters long, 22 kg body mass) than males (1.5 meters long, 70 kg body mass). The researchers suspect that the reduced lifespan for females may be due to the high costs of reproduction including egg production, digging and guarding nests from male Komodo dragons and other predators. While guarding for up to 5 months, the females reduce their feeding and sometimes simply fast resulting in poor physical condition and health.

Scientific American

Laver RJ, Purwandana D, Ariefiandy A, Imansyah J, Forsyth D, Ciofi C, Jessop TS. Life-history and spatial determinants of somatic growth dynamics in Komodo dragon populations. PLoS ONE 7(9): e45398. doi:10.1371/journal.pone.0045398 .

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The paper says that there is a relatively small number of females compared to number of males. Generally small female body size compared to large male body size suggests some sort of harem arrangement, where a male mates with several females. It thus seems likely that most males dragons do not successfully reproduce. Do only a few males each mate with several females? How much is known about breeding structure in dragons.?

By Jim Thomerson (not verified) on 30 Oct 2012 #permalink