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Toads on Lava: Spatial Ecology and Habitat Use of Invasive Cane Toads (Rhinella marina) in Hawai'i.

Ward-Fear G, Greenlees MJ, Shine R - PLoS ONE (2016)

Bottom Line: Because moist sites are scarce on the highly porous lava substrate, Hawai'ian toads depend on anthropogenic disturbance for shelter (e.g. beneath buildings), foraging (e.g. suburban lawns, golf courses) and breeding (artificial ponds).Foraging sites are further concentrated by a scarcity of flying insects (negating artificial lights as prey-attractors).Cane toads in Hawai'i thrive in scattered moist patches within a severely arid matrix, despite a scarcity of flying insects, testifying to the species' ability to exploit anthropogenic disturbance.

View Article: PubMed Central - PubMed

Affiliation: School of Life and Environmental Sciences, Heydon-Laurence Building A08, University of Sydney, Sydney, New South Wales, Australia.

ABSTRACT
Most ecological research on cane toads (Rhinella marina) has focused on invasive populations in Australia, ignoring other areas where toads have been introduced. We radio-tracked and spool-tracked 40 toads, from four populations on the island of Hawai'i. Toads moved extensively at night (mean 116 m, from spool-tracking) but returned to the same or a nearby retreat-site each day (from radio-tracking, mean distance between successive retreat sites 11 m; 0 m for 70% of records). Males followed straighter paths during nocturnal movements than did females. Because moist sites are scarce on the highly porous lava substrate, Hawai'ian toads depend on anthropogenic disturbance for shelter (e.g. beneath buildings), foraging (e.g. suburban lawns, golf courses) and breeding (artificial ponds). Foraging sites are further concentrated by a scarcity of flying insects (negating artificial lights as prey-attractors). Habitat use of toads shifted with time (at night, toads selected areas with less bare ground, canopy, understory and leaf-litter), and differed between sexes (females foraged in areas of bare ground with dense understory vegetation). Cane toads in Hawai'i thrive in scattered moist patches within a severely arid matrix, despite a scarcity of flying insects, testifying to the species' ability to exploit anthropogenic disturbance.

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Related in: MedlinePlus

Microhabitat selection as a function of sex.Figure shows microhabitat use of 40 radio-tracked and spool-tracked cane toads on Hawai’i. The panels show interactions between time (day vs. night) and toad sex: (a) substrate temperature, as recorded with an infrared thermometer (recorded only by day); and (b) the % of bare ground within a 1-m quadrat surrounding the toad. Figure shows mean values and associated standard errors.
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pone.0151700.g005: Microhabitat selection as a function of sex.Figure shows microhabitat use of 40 radio-tracked and spool-tracked cane toads on Hawai’i. The panels show interactions between time (day vs. night) and toad sex: (a) substrate temperature, as recorded with an infrared thermometer (recorded only by day); and (b) the % of bare ground within a 1-m quadrat surrounding the toad. Figure shows mean values and associated standard errors.

Mentions: Interpretation of these patterns is complicated by interactions between time of day, toad sex, and whether or not a site was used by a toad. Nonetheless, most main effects are straightforward because the interactions did not involve reversals of general patterns (Figs 4 and 5). Figs 4 and 5 plot several of these interaction effects. Inspection of the interaction between time (day vs. night) and usage (used vs. available sites) shows that the animals selected areas of relatively bare ground (versus the availability of that habitat type, especially by day: Fig 4b), reflecting their frequent diurnal use of burrows within open areas. Some of those sites were in lava flows, but most radio-tracked toads spent the day in anthropogenically-created retreat-sites, which were cooler than adjacent sites and often, in bare areas shaded by a dense but high understory (Fig 4). A toad’s sex also influenced its habitat use. Female toads were found in areas with more bare ground (Fig 5).


Toads on Lava: Spatial Ecology and Habitat Use of Invasive Cane Toads (Rhinella marina) in Hawai'i.

Ward-Fear G, Greenlees MJ, Shine R - PLoS ONE (2016)

Microhabitat selection as a function of sex.Figure shows microhabitat use of 40 radio-tracked and spool-tracked cane toads on Hawai’i. The panels show interactions between time (day vs. night) and toad sex: (a) substrate temperature, as recorded with an infrared thermometer (recorded only by day); and (b) the % of bare ground within a 1-m quadrat surrounding the toad. Figure shows mean values and associated standard errors.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4814139&req=5

pone.0151700.g005: Microhabitat selection as a function of sex.Figure shows microhabitat use of 40 radio-tracked and spool-tracked cane toads on Hawai’i. The panels show interactions between time (day vs. night) and toad sex: (a) substrate temperature, as recorded with an infrared thermometer (recorded only by day); and (b) the % of bare ground within a 1-m quadrat surrounding the toad. Figure shows mean values and associated standard errors.
Mentions: Interpretation of these patterns is complicated by interactions between time of day, toad sex, and whether or not a site was used by a toad. Nonetheless, most main effects are straightforward because the interactions did not involve reversals of general patterns (Figs 4 and 5). Figs 4 and 5 plot several of these interaction effects. Inspection of the interaction between time (day vs. night) and usage (used vs. available sites) shows that the animals selected areas of relatively bare ground (versus the availability of that habitat type, especially by day: Fig 4b), reflecting their frequent diurnal use of burrows within open areas. Some of those sites were in lava flows, but most radio-tracked toads spent the day in anthropogenically-created retreat-sites, which were cooler than adjacent sites and often, in bare areas shaded by a dense but high understory (Fig 4). A toad’s sex also influenced its habitat use. Female toads were found in areas with more bare ground (Fig 5).

Bottom Line: Because moist sites are scarce on the highly porous lava substrate, Hawai'ian toads depend on anthropogenic disturbance for shelter (e.g. beneath buildings), foraging (e.g. suburban lawns, golf courses) and breeding (artificial ponds).Foraging sites are further concentrated by a scarcity of flying insects (negating artificial lights as prey-attractors).Cane toads in Hawai'i thrive in scattered moist patches within a severely arid matrix, despite a scarcity of flying insects, testifying to the species' ability to exploit anthropogenic disturbance.

View Article: PubMed Central - PubMed

Affiliation: School of Life and Environmental Sciences, Heydon-Laurence Building A08, University of Sydney, Sydney, New South Wales, Australia.

ABSTRACT
Most ecological research on cane toads (Rhinella marina) has focused on invasive populations in Australia, ignoring other areas where toads have been introduced. We radio-tracked and spool-tracked 40 toads, from four populations on the island of Hawai'i. Toads moved extensively at night (mean 116 m, from spool-tracking) but returned to the same or a nearby retreat-site each day (from radio-tracking, mean distance between successive retreat sites 11 m; 0 m for 70% of records). Males followed straighter paths during nocturnal movements than did females. Because moist sites are scarce on the highly porous lava substrate, Hawai'ian toads depend on anthropogenic disturbance for shelter (e.g. beneath buildings), foraging (e.g. suburban lawns, golf courses) and breeding (artificial ponds). Foraging sites are further concentrated by a scarcity of flying insects (negating artificial lights as prey-attractors). Habitat use of toads shifted with time (at night, toads selected areas with less bare ground, canopy, understory and leaf-litter), and differed between sexes (females foraged in areas of bare ground with dense understory vegetation). Cane toads in Hawai'i thrive in scattered moist patches within a severely arid matrix, despite a scarcity of flying insects, testifying to the species' ability to exploit anthropogenic disturbance.

Show MeSH
Related in: MedlinePlus