Encounters between freshwater crocodiles and invasive cane toads in north-western Australia: does context determine impact?

ABSTRACT The potent defensive chemicals of cane toads (Rhinella marina) protect them against predators that lack coevolved physiological tolerance to those toxins. That relative invulnerability may explain why major injuries (such as limb loss) appear to be rare in cane toads from most of their global range; however, we noted frequent predator-induced injuries (>4% of adults) in samples from within the toad’s native range (in French Guiana) and from a site (Lake Argyle) in north-western Australia. Toads at Lake Argyle enter the edge of the lake at night to rehydrate, exposing them to foraging freshwater crocodiles (Crocodylus johnstoni). Crocodiles rarely consume toads, but the attacks often result in loss of a limb. Because limbs contain relatively little toxin, attacks to the limbs expose a crocodile to nauseating but non-lethal amounts of toxin; and hence, facilitate taste aversion learning by the predator. The context of the encounters, such as differences in geography, may help to explain why the invasion of cane toads has not significantly impacted on crocodile populations at this site, in contrast to heavy impacts reported from nearby riverine systems.

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An introduced pentastomid parasite (Raillietiella frenata) infects native cane toads (Rhinella marina) in Panama

Parasitology ◽

10.1017/s0031182014001759 ◽

2014 ◽

Vol 142 (5) ◽

pp. 675-679 ◽

Cited By ~ 6

Author(s):

CRYSTAL KELEHEAR ◽

KRISTIN SALTONSTALL ◽

MARK E. TORCHIN

Keyword(s):

Central America ◽

First Record ◽

Host Shift ◽

Native Range ◽

Host Switch ◽

Rhinella Marina ◽

Introduced Populations ◽

A Site ◽

Hemidactylus Frenatus

SUMMARYThe pentastomid parasite, Raillietiella frenata, is native to Asia where it infects the Asian House gecko, Hemidactylus frenatus. This gecko has been widely introduced and recently R. frenata was found in introduced populations of cane toads (Rhinella marina) in Australia, indicating a host-switch from introduced geckos to toads. Here we report non-native adult R. frenata infecting the lungs of native cane toads in Panama. Eight of 64 toads were infected (median = 2·5, range = 1–80 pentastomids/toad) and pentastomid prevalence was positively associated with the number of buildings at a site, though further sampling is needed to confirm this pattern. We postulate that this pattern is likely due to a host shift of this parasite from an urban-associated introduced gecko. This is the first record of this parasite infecting cane toads in their native range, and the first instance of this parasite occurring in Central America.

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Increased rates of dispersal of free-ranging cane toads (Rhinella marina) during their global invasion

Scientific Reports ◽

10.1038/s41598-021-02828-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Richard Shine ◽

Ross A. Alford ◽

Ryan Blennerhasset ◽

Gregory P. Brown ◽

Jayna L. DeVore ◽

...

Keyword(s):

French Guiana ◽

Native Range ◽

Rhinella Marina ◽

Range Edge ◽

Population Spread ◽

Eastern Australia ◽

Tropical Australia ◽

Free Ranging ◽

Global Invasion ◽

Daily Changes

AbstractInvasions often accelerate through time, as dispersal-enhancing traits accumulate at the expanding range edge. How does the dispersal behaviour of individual organisms shift to increase rates of population spread? We collate data from 44 radio-tracking studies (in total, of 650 animals) of cane toads (Rhinella marina) to quantify distances moved per day, and the frequency of displacement in their native range (French Guiana) and two invaded areas (Hawai’i and Australia). We show that toads in their native-range, Hawai’i and eastern Australia are relatively sedentary, while toads dispersing across tropical Australia increased their daily distances travelled from 20 to 200 m per day. That increase reflects an increasing propensity to change diurnal retreat sites every day, as well as to move further during each nocturnal displacement. Daily changes in retreat site evolved earlier than did changes in distances moved per night, indicating a breakdown in philopatry before other movement behaviours were optimised to maximise dispersal.

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Long distance homing in the cane toad (Rhinella marina) in its native range

Journal of Experimental Biology ◽

10.1242/jeb.243048 ◽

2021 ◽

Author(s):

Daniel A. Shaykevich ◽

Andrius Pašukonis ◽

Lauren A. O'Connell

Keyword(s):

Life Histories ◽

Site Fidelity ◽

French Guiana ◽

Spatial Behavior ◽

Native Range ◽

Short Term ◽

Long Distance ◽

Amphibian Species ◽

Rhinella Marina ◽

Current Paradigm

Many animals exhibit complex navigation over different scales and environments. Navigation studies in amphibians have largely focused on species with life histories that require accurate spatial movements, such as territorial poison frogs and migratory pond-breeding amphibians that show fidelity to mating sites. However, other amphibian species have remained relatively understudied, leaving open the possibility that well-developed navigational abilities are widespread. Here, we measured short-term space use in non-territorial, non-migratory cane toads (Rhinella marina) in their native range in French Guiana. After establishing site fidelity, we tested their ability to return home following translocations of 500 and 1000 meters. Toads were able to travel in straight trajectories back to home areas, suggesting navigational abilities similar to those observed in amphibians with more complex spatial behavior. These observations break with the current paradigm of amphibian navigation and suggest that navigational abilities may be widely shared among amphibians.

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Spatial ecology of cane toads (Rhinella marina) in their native range: a radiotelemetric study from French Guiana

Scientific Reports ◽

10.1038/s41598-021-91262-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jayna L. DeVore ◽

Richard Shine ◽

Simon Ducatez

Keyword(s):

Invasive Species ◽

Body Condition ◽

Spatial Ecology ◽

French Guiana ◽

Source Region ◽

Behavioural Flexibility ◽

Native Range ◽

Environmental Niche ◽

Rhinella Marina ◽

Free Ranging

AbstractLike most invasive species, cane toads have attracted less research in their native range than in invaded areas. We radio-tracked 34 free-ranging toads in French Guiana, a source region for most invasive populations, across two coastal and two rainforest sites. Coastal toads generally sheltered in pools of fresh or brackish water but nocturnally foraged on beaches, whereas rainforest toads sheltered in forested habitats, moving into open areas at night. Over five days of monitoring, native toads frequently re-used shelters and moved little between days (means = 10–63 m/site) compared to invasion-front toads from Australia (~ 250 m). Larger toads moved less between days, but displaced in more consistent directions. At night, foraging toads travelled up to 200 m before returning to shelters. Foraging distance was related to body condition at coastal sites, with toads in poorer body condition travelling farther. Rain increased the probability of coastal toads sheltering in the dry habitats where they foraged. Dispersal and rainfall were lower at coastal sites, and the strategies utilized by coastal toads to minimize water loss resembled those of invasive toads in semi-desert habitats. This global invader already exhibits a broad environmental niche and substantial behavioural flexibility within its native range.

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Long distance homing in the cane toad (Rhinella marina) in its native range

10.1101/2021.06.16.448742 ◽

2021 ◽

Author(s):

Daniel A Shaykevich ◽

Andrius Pasukonis ◽

Lauren A O'Connell

Keyword(s):

Home Range ◽

Life Histories ◽

French Guiana ◽

Spatial Behavior ◽

Native Range ◽

Cane Toad ◽

Short Term ◽

Long Distance ◽

Rhinella Marina ◽

Current Paradigm

Many animals exhibit complex navigation over different scales and environments. Navigation studies in amphibians have largely focused on species with life histories that require advanced spatial capacities, such as territorial poison frogs and migratory pond-breeding amphibians that show fidelity to mating sites. However, other species have remained relatively understudied, leaving the possibility that well-developed navigational abilities are widespread. Here, we measured short-term space use in non-territorial, non-migratory cane toads (Rhinella marina) in their native range in French Guiana. After establishing home range, we tested their ability to return to home following translocations of 500 and 1000 meters. Toads were able to travel in straight trajectories back to home areas, suggesting map-like navigational abilities similar to those observed in amphibians with more complex spatial behavior. These observations break with the current paradigm of amphibian navigation and suggest that navigational abilities may be widely shared among amphibians.

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Antipodean Aftershocks: Group Settlement of Hebridean and non-Hebridean Britons in Western Australia following World War One

Northern Scotland ◽

10.3366/nor.2020.0221 ◽

2020 ◽

Vol 11 (2) ◽

pp. 188-203

Author(s):

Roy Jones ◽

Tod Jones

Keyword(s):

New Zealand ◽

British Empire ◽

Western Australia ◽

The Sun ◽

World War ◽

World War One ◽

A Site

In the speech in which the phrase ‘land fit for heroes’ was coined, Lloyd George proclaimed ‘(l)et us make victory the motive power to link the old land up in such measure that it will be nearer the sunshine than ever before … it will lift those who have been living in the dark places to a plateau where they will get the rays of the sun’. This speech conflated the issues of the ‘debt of honour’ and the provision of land to those who had served. These ideals had ramifications throughout the British Empire. Here we proffer two Antipodean examples: the national Soldier Settlement Scheme in New Zealand and the Imperial Group Settlement of British migrants in Western Australia and, specifically, the fate and the legacy of a Group of Gaelic speaking Outer Hebrideans who relocated to a site which is now in the outer fringes of metropolitan Perth.

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