Ripples
Newsletter of the AUSTRALIAN
PLATYPUS CONSERVANCY
ISSUE 40 - May 2009
OF TIME AND THE
PLATYPUS
In May of last year, a paper announcing
that the sequence of
This project itself was an international
enterprise of mammoth proportions: more than 100 scientists based at 32
universities and research institutes located in nine different countries (
With few exceptions, journalists reporting
on this study were content to explain its findings in terms of the standard
popular concept of the platypus: a weird hybrid between reptiles and “true“
mammals that has been stuck in a static time warp since the age of dinosaurs.
Not surprisingly, the facts actually
revealed by the study are both more complex and a lot more interesting.
To begin with, the majority of platypus
genes (82%) are held in common with a wide range of other vertebrates such as
dogs, mice, chickens, humans and opossums (a marsupial found in
Platypus genes that are held in common
only with other mammals include those coding for the milk proteins known as
caseins. As well as having a nutritional
function, milk proteins also have anti-microbial properties—in fact, it has
been suggested that the reptilian ancestors of mammals may have originally
started producing milk-like substances in order to help protect their eggs from
rotting as well as drying out.
By comparison, the researchers involved in
the platypus genome project seem to have been less successful in identifying
functional genes that the platypus shares only with reptiles.
For example, it turns out that the genes
coding for platypus venom—a cocktail of 19 or more different substances—appear
to have evolved quite independently from those coding for reptile venom, though
both groups seem to have taken advantage of similar chemical pathways to
achieve their ends.
Another example of how the platypus
appears to have evolved in its own right involves its sense of smell. Olfaction is not normally a sense that one
expects to be highly developed in aquatic animals. In keeping with this generalisation, the
platypus has only about half the number of genes linked to odour detection as
compared to land-based mammals.
However, scientists have been intrigued to
learn that this species has an exceptionally large number of genes coding for
specialised smell receptors in the vomeronasal (or Jacobson’s) organ—a
structure present in both mammals and reptiles that is most often used in
social communication. In the case of the
platypus, it has been suggested that these receptors may either serve to detect
chemical signals left by other platypus and/or to help locate underwater prey
based on chemical cues.
Now that the platypus genome has been
mapped, it is much easier to undertake further genetic research on the
species. Accordingly, Ph.D. students have now begun to investigate how
platypus populations in different parts of
We
look forward with great interest to learning about their results.
PLATYPUS COUNT POWERS ON
In Ripples 38 we showed a graph
that compared the average number of platypus seen in visual surveys carried out
on a monthly basis from 2003 to 2006 along the Yarra River (in the Melbourne
suburb of Viewbank) with the average rate at which platypus were captured in
live-trapping sessions in the same catchment.
The two curves were remarkably similar in
shape—platypus sightings and platypus captures both peaked in winter and early
spring. This was ascribed to the fact
that both variables respond to platypus activity, which should increase in
winter for two reasons: (1) platypus have to work harder to find enough food as
water temperatures drop, and (2) adult males become progressively more active
and mobile as the spring breeding season approaches.
Volunteers have been working hard to
provide information for a full-scale Platypus Count visual monitoring
program along the
The shapes of the three curves are very
similar, indicating that enough monitoring was carried out in each area to
provide a valid indicator of platypus activity (which in turn presumably
reflects the number of platypus found there).
In absolute terms, the rate of platypus
sightings at Templestowe was similar to that recorded at Warrandyte throughout
the period that data was available for both locations. By comparison, fewer
sightings occurred at Viewbank, which is located farther downstream than the
other two areas, near the lower geographic limit of where platypus are
regularly found along the Yarra.
With respect to longer term trends, the
average monthly rate of platypus sightings at Viewbank from 2003 to 2006
closely paralleled the rate of sightings recorded there in the first four
months of 2008. In contrast, the
incidence of sightings from May to November 2008 was much lower than in
previous years. It is possible (though
certainly unproven) that the reduced frequency of sightings in the winter and
spring of 2008 may have been causally linked to the unusually low flow regime
experienced along the Yarra through much of this period, e.g. if low flows
contributed to reduced platypus breeding activity.
The use of community-based visual surveys
to track the abundance of platypus populations is necessarily limited to water
bodies where volunteers are available to undertake the work—live-trapping
methods will probably always be required in places supporting few or no human
inhabitants. However, in places where
people do regularly visit waterways, platypus visual monitoring programs
potentially offer numerous advantages over the use of nets:
(1) Far more cost-effective with respect
to generating the large amounts of data needed for reliable monitoring.
(2) Does not entail any risk or
disturbance to the animals.
(3) Less constrained by unpredictable or
bad weather.
(4) Particularly well-suited for use along
larger streams and rivers, i.e. the habitats that are likely to be most
important to platypus conservation in any given catchment.
(5) Intensity of monitoring effort is not
limited by animals learning to recognise and avoid nets (“trap-shyness”).
More research is needed to determine if
the seasonal variation in platypus sightings which predictably occurs along the
The Conservancy is accordingly grateful to
the City of
TRANSLOCATION
UPDATE
If you read Ripples regularly,
you’re probably already aware that platypus are believed to have disappeared
from Cardinia Creek—a small, self-contained stream system located in
Melbourne’s outer southeastern suburbs—in the aftermath of the 1983 “Ash
Wednesday” bushfires which wreaked havoc in the Cardinia Creek valley.
According to local sources, the extinction may have partly reflected the fact
that sections of the creek channel dried up for some time after the fire passed
through the area, presumably due to evaporation.
Since 2004, the Conservancy has been
working to re-establish a viable platypus population along Cardinia Creek, by
translocating young animals from neighbouring water bodies and then monitoring
how well they (and eventually their offspring) have been faring.
Earlier this year, APC staff were dismayed
to learn that at least two members of the new population had been killed in
illegally set crayfish traps (see Ripples 39).
However, the latest and very good news is
that the population is doing its best to bounce back, with six juveniles
captured in a survey session carried out in April. The youngsters comprised two boys and four
girls, christened Peter, Piggy, Peach,
Did You Know That....
Platypus occupy rivers and streams in western
TOOROURRONG
BUSHFIRE DESTRUCTION
Many persons will have fond memories of
the Platypus Insights spotting tours that were run from the
Conservancy’s former research base at
Unfortunately, the very hot bushfire which
ignited near Kilmore in February 2009 destroyed vegetation and manmade
structures throughout the park, including the four bedroom brick residence (a
former caretaker’s cottage) which served as the APC’s base of operations from
1996 to 2007.
It is currently not known how the platypus
living in Toorourrong and two smaller reservoirs located nearby (Wallaby Weir
and Silver Weir) fared in the wake of the inferno.
As discussed in Ripples 39, the
results of a study carried out by APC staff last year suggest that platypus may
generally be expected to survive the direct impacts of bushfire (flames,
radiant heat and smoke) due to their habit of sheltering in burrows located
next to water.
However, the animals’ ongoing survival after the disaster may be more problematic, particularly if a large amount of ash and other loose sediment is washed into the reservoirs and their associated streams this autumn or winter—and this in turn smothers or otherwise severely reduces the number of aquatic insects and other invertebrates that are available for platypus to eat.