As apex predators decline worldwide, there is escalating evidence of their importance in maintaining the integrity and diversity of the ecosystems they inhabit. A transmissible cancer has led to the apparent decline of populations of Tasmanian devils, the apex predator in the Tasmanian ecosystem. A new study in the February issue of Conservation Biology examines the substantial effects of the decline of the Tasmanian devil on terrestrial mammal fauna in Tasmania and sheds light on the critical role apex predators play in maintaining the integrity of ecosystems.

1. © Tracey Hollings
Conservation Biology
Volume 28, Number 1, February 2014
Featured
Paper…

2. Trophic Cascades Following the Disease-Induced
Decline of an Apex Predator, the Tasmanian Devil
Contributed Paper by:
a photo essay…
Conservation Biology
February 2014
Mark Burgman, Editor-in-Chief
www.conbio.org
Published by Wiley
Tracey Hollings
Menna Jones
Nick Mooney
Hamish McCallum

3. ©Rodrigo Hamede
The Tasmanian Devil is threatened with extinction from a
The Tasmanian Devil is threatened with extinction from a
transmissible cancer, devil facial tumor disease.
transmissible cancer, devil facial tumor disease.

4. Trophic cascades following the disease-induced decline of an apex predator, the
Tasmanian Devil
Devil facial tumor disease
(DFTD) has led to apparent
population declines of
Tasmanian Devils in excess of
95% in some areas and has
spread to more than 80% of
their range.
(Hollings, 2013)
Conservation Biology - Vol 28, Issue 1, February 2014

5. ©Georgina Anderson
The Tasmanian devil is the apex mammalian predator in the
The Tasmanian devil is the apex mammalian predator in the
Tasmanian ecosystem. As apex predators disappear worldwide, there
Tasmanian ecosystem. As apex predators disappear worldwide, there
is escalating evidence of their importance in maintaining the integrity
is escalating evidence of their importance in maintaining the integrity
and diversity of the ecosystems they inhabit...
and diversity of the ecosystems they inhabit...
Wild Tasmanian devils at home in a den.
Wild Tasmanian devils at home in a den.

6. DFTD was first detected in the north-east of Tasmania in
1996. Prior to its arrival, devils were widespread and have
been recorded in all Tasmanian vegetation types.
©Ryan Burrows

7. Rapid Ecosystem Change and Polar Bear Conservation
Conservation Letters
Map of Tasmania
showing individual
spotlight survey
transects within
each of 4 regions
representing
different year
ranges of arrival of
DFTD (late, mid,
disease-free,
early). Years are
range of arrival of
DFTD in each
region.
A sub-adult female polar bear on a frozen lake along the shore of Hudson Bay. Small bears
like this are usually wary of adult males which can be predatory.
Hollings, 2013

8. ©Hugh Maguire
©Ryan Burrows
©Ryan Burrows
Unlike mainland Australia, Tasmania retains a nearly
Unlike mainland Australia, Tasmania retains a nearly
intact mammalian fauna community.
intact mammalian fauna community.

9. Trophic cascades following the disease-induced decline of an apex predator, the
Tasmanian Devil
Our results suggest that the decline of
the Tasmanian devil, the apex
mammalian predator in the
Tasmanian ecosystem, has had a
substantial effect on terrestrial
mammal fauna, a result consistent
with evidence from apex predator loss
in other ecosystems
(Hollings, 2013)
Conservation Biology - Vol 28, Issue 1, February 2014

10. Trophic cascades following the disease-induced decline of an apex predator, the
Tasmanian Devil
Maintaining populations of the devil
in the Tasmanian ecosystem, at
densities sufficient to exert top–down
control, may protect populations of
smaller mesopredators…
Conservation Biology - Vol 28, Issue 1, February 2014

11. ©
Tracey Hollings
There is strong compelling evidence to support the
There is strong compelling evidence to support the
assertion that devils can exert top-down control on feral
assertion that devils can exert top-down control on feral
cat populations.
cat populations.

12. ©Tracey Hollings
Feral cats like this one increase in
areas where DFTD has been
present the longest & feral cat
occurrence is significantly and
negatively associated with devils.

13. As devil populations
declined and cats
increased, the smaller
native mesopredator,
the eastern quoll
(pictured), declined, and
there was no sign of
population recovery,
which lead to concerns
for its conservation.
©Menna Jones

14. The best-fitting generalized linear model (GLM) for the mean number of animals per
transect for devils & eastern quolls. The best model, the linear model for feral cats, was
not significantly different from models containing a DFTD arrival variable, so the secondbest model was used to illustrate devil facial tumor disease arrival effects (vertical lines,
period of disease arrival; shaded areas, 95% CIs for GLMs; points, actual values).

15. Trophic cascades following the disease-induced decline of an apex predator, the
Tasmanian Devil
Our results are consistent with assertions that DFTD
causes rapid and severe population decline in devils
that results in substantially reduced apex predator
populations within a few years. There was no
indication of population recovery, and with no
effective management options at present that could
aid recovery of wild populations, the trophic
cascades in the Tasmanian ecosystem resulting
from loss of devils are likely to continue.
Conservation Biology - Vol 28, Issue 1, February 2014

16. ©
Tracey Hollings
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Trophic Cascades Following
the Disease-induced Decline
of an Apex Predator, the
Tasmanian Devil
Note: The February issue is freely
available at:
http://onlinelibrary.wiley.com/journal/10.1111/
(ISSN)1523-1739