‘Boss crocs’ rule complex social system

By Samantha Wheeler 8 May 2013
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Dominant crocodiles rule over large territories and fight off other males, new research suggests.

CROCODILES EXIST UNDER A complex social hierarchy, a new study has revealed, which revolves around a dominant alpha croc.

The new findings support the theory that an alpha, or ‘boss croc’, rules over a geographical area, while subordinate males travel much further to find a mate than previously thought.

“The findings show that crocodiles are far more mobile than we previously considered, and that they exist within a complex social hierarchy,” says lead researcher Dr Hamish Campbell, at the University of Queensland.

Crocodiles: social interactions and hierarchy

The study used satellite tagging to record the location and movement of male and female estuarine crocodiles (Crocodylus porosus) during the breeding and nesting season.

Researchers say the findings, published recently in the journal PLOS ONE, suggest that each boss croc dominates a territory of around 7-12 sq. km.

Subordinate males bore scars and were found to move very quickly through certain territories, covering up to 1000km in six months, leading researchers to suggest they are aggressively excluded by dominant males.

Professor Gordon Grigg, a biologist from the University of Queensland, says boss crocs can be extremely territorial.

“Studies in the Northern Territory have shown that dominant crocs tend to have a calming influence on all the others – they keep them in check,” says Gordon.

Incredibly, Gordon also says that previous studies show relocated crocodiles eventually return to their homes.

“One of the animals was moved across Cape York,” Gordon remembers. “It spent two or three months hanging around where it had been released and then swam up the east coast, through Torres Strait, down the west coast and back to the same river where it was caught.”

Removal of crocs for public safety a bad idea?

The findings have led researchers to suggest that moving aggressive males out of their habitat may not actually be in the interest of public safety. Relocating a dominant male could cause social upsets, says Hamish, or even an influx of competitive males from neighbouring areas.

“We need further research to fully understand the implications of management interventions upon the social dynamics of estuarine crocodiles,” says Hamish.

Gordon agrees that taking dominant males out of their territory may attract more aggressive crocodiles, and may encourage aggression within the existing population.

“The more we know about their behaviour and movement, the more likely it is that people are going to be able to make good recommendations about how to manage public safety,” he says.