| 11. |
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| 12. |
- Hagman, Mattias, et al.
(author)
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Alarm cues experienced by cane toad tadpoles affect post-metamorphic morphology and chemical defences
- 2009
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In: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 23, s. 126-132
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Journal article (peer-reviewed)abstract
- Summary: In many anuran species, larvae modify their developmental trajectories and behaviour in response to chemical cues that predict predator risk. Recent reviews highlight a dearth of studies on delayed (post-metamorphic) consequences of larval experience. 2 We raised cane toad (Bufo marinus) tadpoles either under control conditions or in the presence of non-lethal predator cues (crushed conspecifics). 3 Exposure to these chemical cues massively reduced size at metamorphosis, as predicted by theory. Parotoid glands were larger relative to body size in post-metamorphic animals from the experimental treatment, suggesting higher investment in chemical defences. 4 Exposure to chemical cues from crushed conspecifics during larval life reduced total bufadienolide content of metamorphs, but increased amounts of one specific bufadienolide (bufalin). 5 Hence, cane toads respond to perceived predation risk in the aquatic environment by metamorphosing at a smaller size and modifying their investment in defensive toxins during post-metamorphic life. 6 Phenotypically flexible responses to larval conditions vary among amphibian taxa, and can involve significant carry-over effects into post-metamorphic life.
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| 13. |
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| 14. |
- Hagman, Mattias, et al.
(author)
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Australian tadpoles do not avoid chemical cues from invasive cane toads (Bufo marinus)
- 2008
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In: Wildlife research (East Melbourne). - 1035-3712 .- 1448-5494. ; 35:4, s. 59-64
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Journal article (peer-reviewed)abstract
- In previous work, we have shown that tadpoles of invasive cane toads (Bufo marinus) strongly avoid scent cues from crushed conspecific tadpoles. Thus, identifying the identity of the chemical involved may provide novel approaches to toad control, by manipulating the behaviour of toad tadpoles. A first step in the search for that chemical is to see whether toad tadpoles are similarly repelled by chemical cues from crushed tadpoles of other species. Our experimental trials with four native Australian frogs (three hylids, one myobatrachid) show that toads do not respond to chemical cues from these taxa. Hence, the specific chemicals that induce avoidance cannot be generic ones (e.g. body fluids, tissue fragments) but instead, must reflect some underlying chemical divergence in body composition between the tadpoles of cane toads versus the other anurans that we have tested.
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| 15. |
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| 16. |
- Hagman, Mattias
(author)
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Control methods for unwanted anurans
- 2011
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Book (peer-reviewed)abstract
- Anurans (frogs and toads) worldwide are threatened by habitat loss, emerging infectious diseases, overexploitation, pollution, climatic change and introduction of exotic species. As a result of human activities, some anurans have actually increased their distribution and are now doing extremely well in places far outside of their natural range. But these anurans are often unwanted in the introduced range because they may disturb recipient ecosystems and pose a threat to indigenous fauna, including native amphibians. This book reviews anuran biology and discusses some life history traits that may be suitable for targeted control measures.
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| 17. |
- Hagman, Mattias, et al.
(author)
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Correlated evolution of conspicuous colouration and body size in the poison frog family Dendrobatidae
- 2003
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In: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 57:12, s. 2904-2910
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Journal article (peer-reviewed)abstract
- Conspicuous coloration is often used in combination with chemical defenses to deter predators from attacking. Experimental studies have shown that the avoidance inducing effect of conspicuous prey coloration increases with increasing size of pattern elements and with increasing body size. Here we use a comparative approach to test the prediction from these findings, namely that conspicuous coloration will evolve in tandem with body size. In our analysis, we use a previously published mitochondrial DNA-based phylogeny and comparative analysis of independent contrasts to examine if evolutionary shifts in color pattern have been associated with evolutionary changes in body size in aposematic poison frogs (Anura: Dendrobatidae). Information on body size (snout to vent length) and coloration were obtained from the literature. Two different measures of conspicuousness were used, one based on rankings by human observers and the other based on computer analysis of digitized photographs. The results from comparative analyses using either measure of coloration indicated that avoidance inducing coloration and body size have evolved in concert in poison frogs. Results from reconstruction of character change further indicate that the correlated evolution of size and coloration has involved changes in both directions within each of the different clades of the phylogenetic tree. This finding is consistent with the hypothesis that selection imposed by visually guided predators has promoted the evolution of larger body size in species with conspicuous coloration, or enhanced evolution of conspicuous coloration in larger species.
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| 18. |
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| 19. |
- Hagman, Mattias, et al.
(author)
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Deceptive digits : the functional significance of toe waving by cannibalistic cane toads (Bufo marinus)
- 2008
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In: Animal Behaviour. - : Elsevier BV. - 0003-3472 .- 1095-8282. ; 75, s. 123-131
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Journal article (peer-reviewed)abstract
- Many ambush foraging predators possess specialized structures and behaviours that plausibly function to attract prey, but this hypothesis has rarely been subject to direct empirical tests. If luring evolved to attract specific prey types then we predict that it will be manifested only if that prey type is present, and only by predators of the size class that feed on that prey type. Also, luring should induce closer approach by prey; and aspects of the behaviour (e. g. frequency of movement of the lure) should have been. ne tuned by selection to induce maximal response from prey. We describe a novel luring system: small- and medium-sized ( but not metamorph and large) cane toads, Chaunus marinus, wave the long middle toe of the hind-foot up and down in an obvious display. In keeping with the functional hypothesis, toe waving is elicited by moving edible-sized objects such as crickets or metamorphic toads. Metamorphic toads are attracted to this stimulus, and trials with a mechanical model show that both the colour and the vibrational frequency of the toe correspond closely with those most effective at attracting smaller conspecifics towards the lure. The independent evolution of visual luring systems in many animal lineages provides a powerful opportunity for robust empirical tests of adaptive hypotheses about signal design.
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| 20. |
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