Evolution of fighting (Enquist & Leimar, 1983 ) Previous research on crabs

› Size of body and claws (Sneddon, Huntingford, Taylor & Orr, 2000)

› Strength (Gabbanini, Gherardi &Vannini, 1995)› Sex, presence of food and receptive female

(Jachowski, 1974) Sinclair (1977) found that when in pairs, one crab

always exerted dominance › Typically larger crabs were more dominant than

smaller› Males dominant over the females› Similar size and same sexed crabs were more likely

to fight

The smaller the environment the more aggressive behaviour crabs will display

Species – Broadfooted Mangrove Crab (Metopograpsus frontalis)› 5 female and 5 male

An “arena” was created for the crabs› 3 dimensions – large (82x82 cm), medium

(56.4x56.4 cm) & small (39x39 cm) Crabs placed in centre of arena for three

minutes to observe behaviour For every initial reaction a tally was

made.

SMALL

MEDIUM

LARGE

THE ARENAS

Pinching Penelope(3 cm)

Jackie(3 cm)

Vicious Victoria(4 cm)

Crabby Patty(2 cm)

Ariel(3.2)

Kane The Warrior King(4 cm)

Frisky Freddie(2.8 cm)

Bone Crusher(4 cm)

King Triton(3.4 cm)

Sgt. Slaughter(3.8 cm)

BIG BERTHA(7.4 cm)

Let the fighting begin – DING DING DING!

Bubbled Loud clicking Ran to corners Medium to large (2.8 cm – 4 cm) Greater amount of contact

› Walked over each other

Bubbled Clicking was not very loud Ran to corners Small to large (2 cm – 4 cm)

› **Except for Big Bertha: 7.4 cm

Hypothesis disproved› More aggression was shown in the

larger arena than the smaller arena Sneddon, Huntingford, Taylor & Orr

(2000) found that size did not matter, however, we saw more attacks from larger crabs

As Sinclair (1977) found, › the males were more aggressive than the

females

Crabs were less aggressive in the smaller arena› The smaller arena is more like their

home environment (under rocks in muddy-sand areas)

› First placed in the largest arena

Examine…› Different Species

Complete more trials Use different arenas—more like home Use new crabs in every arena to

eliminate over-exposure Switch order of arenas Aggressive behaviour only for territory?

Darnell, RM. (1971). In ‘Organism and Environment’. (Ed. D Kennedy and R.B. Park) pp. 97. (W.H. Freeman and Company: San Francisco, CA, USA.)

Davie, P. (1998). In ‘Wild Guide to Moreton Bay’. (Ed. Michelle Ryan) pp. 47. (Queensland Museum: South Brisbane, QLD.)

Enquist, M & Leimar, O. (1983). Evolution of Fighting Behaviour: Decision Rules Assessment of Relative Strength. Journal of Theoretical Biology. 102, 387-410.

Gabbanini F, Gherardi F, Vannini M. (1995). Force and dominance in the agonistic behavior of the freshwater crab Potamon fluviatile. Aggressive Behavior. 21, 451-462.

Jachowski, RL. (1974). Agonistic Behavior of the Blue Crab, Callinectus sapidus Rathbun. Bahaviour. 50, 232-253.

Sinclair, ME. (1977). Agonistic behavior of the stone crab, Menippe mercenaria (Say). Animal Behaviour. 25, 193-207.

Sneddon LU, Huntingford FA, Taylor AC, Orr JF. (2000). Weapon strength and competitive success in the fights of shore crabs (Carcinus maenas). Journal of Zoology. 250, 397-403.

Thank you to the UQ Moreton Bay Research Centre, Dr. Janet Lanyon,

all the tutors, and Tom.