I received my formal education in South Africa. During my graduate years I worked on the breeding behaviour of several species of frogs. After my PhD I switched to studying fiddler crabs and completed three post-docs. I then did a year of lecturing in South Africa before moving to Panama to work for the Smithsonian for the next six years, still studying fiddlers. I took up my present post as lecturer at ANU at the start of 2002. All of this experience has forged me into the truly brilliant scientist that I am.
My current research is entirely field-based and I have spent many hours sitting on sunny beaches staring at amazing little crabs. Most of my fieldwork has been carried out in Mozambique, Japan, South Africa and Central America. I am now working on tropical Australian fiddlers. My main study site is in Darwin, NT.
I work on the behavioural ecology of fiddler crabs. There are over 100 species of fiddlers world wide, and about 20 of them occur in Australia. They are often the most commonly seen inter-tidal animal on tropical mudflats, and are ecologically important as a major food source for shore birds. Although a lot is known about them as prey items, surprisingly little is known about their behaviour. They are ideal study animals because they occur in huge numbers and are exceptionally easy to catch, mark, observe and manipulate. They are sexually dimorphic, males having a single enlarged claw which is used both as a weapon and waved to attract mate-searching females. My work has covered a broad range of topics but I have concentrated on three main areas:
The mate choice process
I am particularly interested in the process of mate selection. In most animal species, females have inherent mating preferences that can be demonstrated in simple laboratory studies involving two-choice tests. Under natural conditions, however, the actual process of mate choice is far more complex. There are many constraints that may prohibit females from expressing their preferences. They may face temporal or energetic constraints on free choice. Predation risk or variation in the quality of resources they encounter may affect their final choice. Similarly, variation in the social environment, such as male-male competition, levels of male phenotypic variation or operational sex ratios could influence their selection of mates. Much of my research focuses on the biotic and abiotic factors that determine the level at which females are able to express their underlying mating preferences.
In animal communication it is generally true that the signals animals use convey accurate and honest information. Individuals of some species, however, produce deceptive signals that provide inaccurate information. This "cheating" may allow the signaller to attract mates or repel competitors when it would be incapable of doing so were it to signal honestly. Some fiddler crabs appear to signal deceptively. Fiddlers can autotomise their large claw and, through a series of moults, regenerate a new one. In most fiddler species, the regenerated claw is identical to the original. In some species, however, the regenerated claw is clearly different. It lacks teeth, has a smaller muscle mass and more delicate fingers. Males apparently quickly regenerate their claw to the same overall length as the original, but produce a cheaper version. This is less effective as a weapon but is lighter and therefore more easily waved. The regenerated claw appears to act as an effective visual bluff of fighting ability and may actually be preferred by mate searching females. I am presently investigating this apparent case of cheating.
Fighting neighbours and strangers
Male fiddlers use their enlarged claws in fights. First they threaten each other with aggressive waves, then they push each other with the front surface of the claw, and finally they interlock claws and grapple until one male, the loser, is flicked away. Territory owners fight approaching strangers that try to usurp their territories. They also fight neighbours to negotiate and demarcate territory boundaries. Strangers pose a greater threat than neighbours because losing a fight with a stranger means losing the entire territory whereas losing a fight with a neighbour only results in a slight reduction in territory size. In other animals, fights with both strangers and neighbours are thought to be tests of strength with the stronger male most likely to win. Oddly, in fiddler crabs, this does not appear to be the case. Fights between neighbours do not appear to be settled by brute force. Instead, it appears that residents use aggression as a sort of punishment against encroaching neighbours. The fight itself inflicts time and energy costs on the neighbour so, by consistently engaging the neighbour in a fight each time it encroaches, residents may decrease the likelihood of the neighbour returning to the disputed area. If this is true, then fights between neighbours and those between strangers are fundamentally different interactions. While strangers might fight to win, neighbours may not be trying to 'beat' the encroacher but rather to 'nag' it into respecting the border between them.
- 2013- Associate Editor, Methods in Ecology & Evolution; British Ecological Society / Wiley
- 2013- Editor, Animal Behaviour; Elsevier
- 2007-2012 Consulting Editor, Animal Behaviour; Elsevier
- 2004-2007 Associate Editor, Behavioural Ecology & Sociobiology; Springer.
- Booksmythe, Isobel; Backwell, Patricia R. Y.; Jennions, Michael D,. Competitor size, male mating success and mate choice in eastern mosquitofish, Gambusia holbrooki Animal Behaviour 85 (2) 371-375 Published: FEB 2013
- Bolton, Jessica; Backwell, Patricia R. Y.; Jennions, Michael D,. Density dependence and fighting in species with indeterminate growth: a test in a fiddler crab Animal Behaviour 85 (6) 1367-1376 Published: JUN 2013
- Hayes, Catherine L.; Booksmythe, Isobel; Jennions, Michael D.; et al., Does male reproductive effort increase with age? Courtship in fiddler crabs Biology Letters 9 (2 Published: APR 23 2013
- Callander, Sophia; Hayes, Catherine L.; Jennions, Michael D.; et al., Experimental evidence that immediate neighbors affect male attractiveness Behavioral Ecology 24 (3) 730-733 Published: MAY-JUN 2013
- Johnson, Laura; Mantle, Beth L.; Gardner, Janet L.; et al, Morphometric measurements of dragonfly wings: the accuracy of pinned, scanned and detached measurement methods Zookeys (276) 77-84 Published: 2013
- Kahn, Andrew T.; Dolstra, Tegan; Jennions, Michael D.; et al,. Strategic male courtship effort varies in concert with adaptive shifts in female mating preferences Behavioral Ecology 24 (4) 906-913 Published: JUL-AUG 2013
- Callander, Sophia; Kahn, Andrew T.; Hunt, John; et al., The effect of competitors on calling effort and life span in male field crickets Behavioral Ecology 24 (5) 1251-1259 Published: SEP-OCT 2013
- Callander, Sophia; Kahn, Andrew T.; Maricic, Tim; et al., Weapons or mating signals? Claw shape and mate choice in a fiddler crabBehavioral Ecology and Sociobiology 67 (7) 1163-1167 Published: JUL 2013
- Callander, Sophia; Bolton, Jessica; Jennions, Michael D.; et al,. A farewell to arms: males with regenerated claws fight harder over resources Animal Behaviour 84 (3) 619-622 Published: SEP 2012
- Callander, Sophia; Backwell, Patricia R. Y.; Jennions, Michael D. Context-dependent male mate choice: the effects of competitor presence and competitor size Behavioral Ecology 23 (2) 355-360 Published: MAR-APR 2012.