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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

General habitat use by toads on the island of Hawai’i.On the leeward (dry) side of Hawai’i, dense populations of cane toads were found only in artificially irrigated areas like this golf course (a); but toads tracked at these sites often used crevices in adjacent lava flows as diurnal retreat sites (b). Observations and dissections suggest that cockroaches were the most important prey type for all toad populations that we studied (c). Photographs by M. Greenlees (a,b) and G. Clarke (c).
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pone.0151700.g001: General habitat use by toads on the island of Hawai’i.On the leeward (dry) side of Hawai’i, dense populations of cane toads were found only in artificially irrigated areas like this golf course (a); but toads tracked at these sites often used crevices in adjacent lava flows as diurnal retreat sites (b). Observations and dissections suggest that cockroaches were the most important prey type for all toad populations that we studied (c). Photographs by M. Greenlees (a,b) and G. Clarke (c).

Mentions: The distinctive landforms and climate of Hawai’i impose strong restrictions on anurans (Fig 1). Due to the islands’ volcanic origin, the substrate is composed of highly porous lava; thus, damp retreat-sites are scarce. Rainfall is high and relatively aseasonal on the eastern windward (wet) side of the major islands, but extensive rain-shadows create severely arid conditions on the western leeward (dry) side [19]. Even on the wet side of each island, natural permanent waterbodies are rare. Allied to that scarcity, the depauperate native insect fauna of Hawai’i offers limited feeding opportunities for a generalist insectivore such as the cane toad. For example, artificial lights attract swarms of flying insects (at least seasonally) in many parts of the tropics, but not in Hawai’i (see below for quantification of this pattern). However, anthropogenically modified habitat provides both water and insect food. On the wet side of the island of Hawai’i, frequent rainfall allows toads to move extensively through the landscape to exploit favorable (human-subsidized) resource patches; but on the dry side, toads are primarily restricted to artificially-watered habitats such as golf courses.


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)

General habitat use by toads on the island of Hawai’i.On the leeward (dry) side of Hawai’i, dense populations of cane toads were found only in artificially irrigated areas like this golf course (a); but toads tracked at these sites often used crevices in adjacent lava flows as diurnal retreat sites (b). Observations and dissections suggest that cockroaches were the most important prey type for all toad populations that we studied (c). Photographs by M. Greenlees (a,b) and G. Clarke (c).
© Copyright Policy
Related In: Results  -  Collection

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

pone.0151700.g001: General habitat use by toads on the island of Hawai’i.On the leeward (dry) side of Hawai’i, dense populations of cane toads were found only in artificially irrigated areas like this golf course (a); but toads tracked at these sites often used crevices in adjacent lava flows as diurnal retreat sites (b). Observations and dissections suggest that cockroaches were the most important prey type for all toad populations that we studied (c). Photographs by M. Greenlees (a,b) and G. Clarke (c).
Mentions: The distinctive landforms and climate of Hawai’i impose strong restrictions on anurans (Fig 1). Due to the islands’ volcanic origin, the substrate is composed of highly porous lava; thus, damp retreat-sites are scarce. Rainfall is high and relatively aseasonal on the eastern windward (wet) side of the major islands, but extensive rain-shadows create severely arid conditions on the western leeward (dry) side [19]. Even on the wet side of each island, natural permanent waterbodies are rare. Allied to that scarcity, the depauperate native insect fauna of Hawai’i offers limited feeding opportunities for a generalist insectivore such as the cane toad. For example, artificial lights attract swarms of flying insects (at least seasonally) in many parts of the tropics, but not in Hawai’i (see below for quantification of this pattern). However, anthropogenically modified habitat provides both water and insect food. On the wet side of the island of Hawai’i, frequent rainfall allows toads to move extensively through the landscape to exploit favorable (human-subsidized) resource patches; but on the dry side, toads are primarily restricted to artificially-watered habitats such as golf courses.

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