Kangaroo Island ants 'play dead' to avoid predators

Date:
May 9, 2023
Source:
University of South Australia
Summary:
They're well known for their industrious work, but now a species
of ant on Kangaroo Island is also showing that it is skilled at
'playing dead', a behavior that researchers believe is a recorded
world first.


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FULL STORY ========================================================================== They're well known for their industrious work, but now a species of ant
on Kangaroo Island is also showing that it is skilled at 'playing dead',
a behaviour that University of South Australia researchers believe is
a recorded world first.

Accidentally discovered as researchers were checking pygmy-possum and
bat nest boxes on Kangaroo Island, a colony of Polyrhachis femorata ants appeared to be dead... until one moved.

Researchers believe the ants were 'playing dead' as a defensive strategy
to avoid potential danger.

Published by CSIRO, this is the first time that a whole colony of ants
has been recorded feigning death, and the first record of the Polyrhachis femorataant species for South Australia.

Wildlife ecologist, UniSA's Associate Professor S. 'Topa' Petit, says
she was surprised to discover a colony of what appeared to be dead ants
in one of the nest boxes.

"The mimicry was perfect," Assoc Professor Petit says. "When we opened
the box, we saw all these dead ants...and then one moved slightly.

"This sort of defensive immobility is known among only a few ant
species -- in individuals or specific casts -- but we don't know of
other instances when it's been observed for entire colonies.

"In some of the boxes containing colonies of Polyrhachis femorata, some individuals took a while to stop moving, and others didn't stop. The
triggers for the behaviour are difficult to understand." Assoc Prof
Petit says that nest boxes may present an opportunity to study the ants' death-feigning behaviours, which are of great interest to many behavioural ecologists investigating a diversity of animal species.

The discovery was made during the Kangaroo Island Nest Box Project, where
901 box cavities have been monitored across 13 diverse properties as part
of wildlife recovery efforts following the devastating 2020 bushfires.

Co-researcher at the Kangaroo Island Research Station, Peter Hammond, says
that he used to call the Nest Box Project 'Friends of the Invertebrates', because invertebrates were often the only occupants of the bat and
pygmy-possum nest boxes.

"We are learning a lot about invertebrates as well as targeted
vertebrates," Hammond says.

"Most of our several hundred boxes are on burnt ground, but we also have
some on unburnt properties as controls because our aim is to determine
the value of nest boxes in bushfire recovery.

"Polyrhachis femorata is strongly associated with the critically
endangered Narrow-Leaf Mallee community, where it colonised several
boxes very quickly.

However, we also have records for two other properties further west,
indicating that the ants will use other habitats.

"We believe that the Polyrhachis femorata species was strongly affected
by the bushfires." Assoc Prof Petit says there is a lot to discover
about this species.

"Polyrhachis femorata is a beautiful arboreal ant that tends to be
quite shy, but little else is known about its ecology or behaviour,"
Assoc Prof Petit says.

"We have a relatively unknown world of ants under our feet and in
the trees.

Ants provide crucial ecosystem services and are a vital part of functional ecosystems on Kangaroo Island and elsewhere.

"It is very exciting that such an endearing species as Polyrhachis
femorata is living on Kangaroo Island and we look forward to finding
out more about its ecology.

"We have no doubt that other ants with similar death-feigning behaviours
will be discovered in Australia, but it is thrilling to be among the
pioneers."
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========================================================================== Story Source: Materials provided by University_of_South_Australia. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Sophie Petit, Peter A. Hammond, Brian Heterick, John J. Weyland.

Polyrhachis femorata (Hymenoptera: Formicidae) habitat and colony
defensive immobility strategy. Australian Journal of Zoology,
2023; 70 (4): 126 DOI: 10.1071/ZO22042 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/05/230509122125.htm

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