| 1. |
- Hagman, Mattias, et al.
(författare)
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Australian tadpoles do not avoid chemical cues from invasive cane toads (Bufo marinus)
- 2008
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Ingår i: Wildlife research (East Melbourne). - 1035-3712 .- 1448-5494. ; 35:4, s. 59-64
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Hagman, Mattias, et al.
(författare)
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Deceptive digits : the functional significance of toe waving by cannibalistic cane toads (Bufo marinus)
- 2008
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Ingår i: Animal Behaviour. - : Elsevier BV. - 0003-3472 .- 1095-8282. ; 75, s. 123-131
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Hagman, Mattias, et al.
(författare)
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Effects of invasive cane toads on Australian mosquitoes : does the dark cloud have a silver lining?
- 2007
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Ingår i: Biological Invasions. - : Springer Science and Business Media LLC. - 1387-3547 .- 1573-1464. ; 9:4, s. 445-452
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Tidskriftsartikel (refereegranskat)abstract
- Research on the ecological impacts of invasive organisms typically looks only for negative impacts, ignoring the possibility that the wider community might see benefits in some of these effects. To truly understand the impact of invasive species, we need to look as broadly as possible, and incorporate studies on a diversity of variables. The spread of the South American cane toad (Bufo marinus) through tropical Australia is widely viewed as an ecological catastrophe, but anecdotal reports suggest that the invasion of toads may reduce the numbers of mosquitoes (and thus, potentially, the risk they pose to human health). We conducted experiments to determine whether the presence of toad tadpoles affects survival rates, adult body sizes and/or rates of oviposition of four species of disease-carrying mosquitoes. In the laboratory, the presence of toad tadpoles significantly reduced the sizes of adult mosquitoes at emergence, and also reduced survival rates of the larvae of one mosquito species. In field trials, mosquitoes were less likely to oviposit in waterbodies containing toad tadpoles. Accordingly, these data suggest (but do not prove) that toad invasion may reduce mosquito abundance. More generally, any overall evaluation of the impact of an invasive species needs to consider possible benefits (e.g. to human health) as well as negative effects (e.g. to native species). Both types of information are essential to inform community decisions about the management of feral taxa such as the cane toad in Australia.
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| 4. |
- Hagman, Mattias, et al.
(författare)
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Spawning-site selection by feral cane toads (Bufo marinus) at an invasion front in tropical Australia
- 2006
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Ingår i: Austral ecology (Print). - : Wiley. - 1442-9985 .- 1442-9993. ; 31:5, s. 551-558
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Tidskriftsartikel (refereegranskat)abstract
- Spawning sites are a critical and often scarce resource for aquatic-breeding amphibians, including invasive species such as the cane toad (Bufo marinus). If toads select spawning sites based on habitat characteristics, we can potentially manipulate those characteristics to either enhance or reduce their suitability as breeding sites. We surveyed 25 spawning sites used by cane toads, and 25 adjacent unused sites, in an area of tropical Australia recently invaded by these feral anurans. Water chemistry (pH, conductivity, salinity, turbidity) was virtually identical between the two sets of waterbodies, but habitat characteristics were very different. Toads selectively oviposited in shallow pools with gradual rather than steep slopes, and with open (unvegetated) gradually sloping muddy banks. They avoided flowing water, and pools with steep surrounds. In these respects, cane toads broadly resemble previously studied toad species in other parts of the world, as well as conspecifics within their natural range in South America.
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| 5. |
- Hagman, Mattias, et al.
(författare)
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Understanding the toad code : behavioural responses of cane toad (Chaunus marinus) larvae and metamorphs to chemical cues
- 2008
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Ingår i: Austral Ecology. - : Wiley. - 1442-9985. ; 33:1, s. 37-44
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Tidskriftsartikel (refereegranskat)abstract
- Larvae of many anuran taxa display strong behavioural responses to chemical cues, including alarm signals from injured conspecific tadpoles. We exposed tadpoles and metamorphs from an Australian population of the invasive cane toad (Chaunus [Bufo] marinus) to a range of chemical stimuli and quantified their responses both in the laboratory and in the field. Filtered fluids containing scent cues from crushed conspecifics elicited strong avoidance from tadpoles, whereas other cues (e.g. scent of food, of native-range fish or urodele predators, and thermal stimuli) did not. Apparent aggregation of tadpoles in response to scent cues proved to be an artifact of tank design, and was an indirect consequence of avoidance of those cues. Field trials confirmed that free-ranging toad tadpoles and metamorphs avoided chemical cues from crushed conspecifics, suggesting that the chemicals inducing this response might provide an opportunity to develop targeted control methods for this invasive species.
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| 6. |
- Kelehear, Crystal, et al.
(författare)
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Interactions between infective helminth larvae and their anuran host
- 2011
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Ingår i: Herpetologica. - 0018-0831 .- 1938-5099. ; 67:4, s. 378-385
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Tidskriftsartikel (refereegranskat)abstract
- Detailed observations on interactions between parasites and prospective hosts during the infection process can clarify (1) the routes by which parasites enter the host and (2) the ability of prospective hosts to detect, avoid, or resist potential parasites. Such information can clarify determinants of host vulnerability. Infective larvae of the nematode Rhabdias pseudosphaerocephala entered the bodies of their anuran host the Cane Toad (Rhinella marina, formerly Bufo marinus) primarily through the orbit (i.e., by crawling over the surface of the toad's eye) rather than by burrowing through the skin (believed to be the usual route of infection for rhabditid parasites). In our experimental infections, metamorph Cane Toads detected infective R. pseudosphaerocephala larvae but did not avoid them, nor did they manage to restrict rates of infective larvae penetration by using behavioral means (the toads kicked at infective larvae but failed to dislodge them). Rhabdias pseudosphaerocephala cause damage to their toad host during the process of host entry and throughout the ensuing infection. Despite the high cost of infection and the low cost of avoidance, metamorph Cane Toads seem to lack effective parasite avoidance strategies.
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