SCIENCE MAG (Washington, DC) 01 March 11 Dark Shells Make for Mean Tortoises (John C. Cannon)
The next time a tortoise crosses your path, check out his shell. If it has lots of dark patches, give him a wide berth. When a team of researchers pitted two male Hermann's tortoises against each other, the one with more dark splotches on his shell was more apt to pick a fight. Heavily splotched tortoises also weren't as shy about approaching a potential predator—in this case, a human—to snatch a proffered apple, the team reports in an upcoming issue of Animal Behaviour. Color and aggressiveness may be genetically linked, the researchers say, with the same gene or set of genes coding for both traits. Or, higher amounts of the pigment melanin allow tortoises with more black shell spots to absorb extra sunlight to keep their body temperatures up, which may leave them more energy to throw into impudently defending their territory.

Animal Behaviour, Volume 81, Issue 4, April 2011, Pages 859-863
Melanin-based coloration predicts aggressiveness and boldness in captive eastern Hermann’s tortoises Alia Maflia, Kazumasa Wakamatsub, 1 and Alexandre Roulina, ,
a Department of Ecology and Evolution, University of Lausanne, Switzerland
b School of Health Sciences, Fujita Health University, Japan
Received 22 June 2010; revised 20 September 2010; accepted 25 January 2011. MS. number: 10-00446R. Available online 23 February 2011.
Although body coloration is often used in social interactions, few studies have tested whether it is linked to a suite of behavioural traits. We examined whether among captive adult male eastern Hermann’s tortoises, Eurotestudo boettgeri, behavioural patterns covary with eumelanic coloration of the shell. Dark eumelanic males were more aggressive in male–male confrontations and bolder towards humans. These relationships were independent of body size and ambient temperature. Activity level and exploration were not significantly associated with coloration. We conclude that, at least in captivity, melanic shell coloration predicts agonistic behaviour towards conspecifics and fearfulness towards humans (i.e. boldness).
Dark Shells Make for Mean Tortoises

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