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 1997 Research
reports
- Metabolic and hormonal
relations of arid-zone passerines
- Heartsize and mitochondrial
density in red Kangaroos and feral Goats: A comparison of exercise
capacities
- An evaluation of the controls
on hillslope sediment transport in a small Australian arid zone
catchment: a case study from Homestead Creek catchment, western
New South Wales, Australia
- Morphological and metabolic
responses of male White-plumed Honeyeaters to exogenous testosterone
- Thermoregulation by kangaroos
from mesic and arid habitats: Influence of temperature on routes
of heat loss in Grey Kangaroos (Macropus giganteus) and
Red Kangaroos (Macropus rufus)
- Hydrology and erosion
mechanisms in patterned chenopod shrublands
- Energetics and biomechanics
of locomotion by Red kangaroos (Macropus rufus)
- Food selection by the
Euro (Macropus robustus erubescens)
- The quantitative assessment
of Bladder Saltbush (Atriplex vesicaria) in rangelands
using remotely sensed imagery at Fowlers Gap Station
- Nest-site spacing and selection,
diet and parental care of the Wedge-tailed Eagle (Aquila audax)
at Fowlers Gap
- Re-introduction of hand-reared
Red Kangaroos (Macropus rufus)
- The sociogenetic organisation
of Rhytidoponera sp, 12 (Formicidae: Ponerinae)
- Flight behaviour and cooperation
of female kangaroos with their young-at-foot: A comparison between
species
Investigators: Lee Astheimer1, William A. Buttemer1,
& Gordon Rogowitz2
1Dept of Biomedical and Biological Sciences, Univ.
of Wollongong
2Dept. of Biology, University of Puerto Rico
We measured basal metabolic rate of selected
old endemic Australian species (e.g., Chestnut-crowned Babblers,
White-plumed Honeyeaters, Singing Honeyeaters, Spiny-cheeked Honeyeaters,
Variegated Wrens) and Zebra Finches (new endemic). Contrary to
the literature, we found no evidence of reduced metabolic rate
in any of the old-endemic species which showed BMR values that
were statistically indistinguishable from predictions based on
data from north-hemisphere passerines. We also examined reproductive
steroid levels in free-living honeyeaters and fairy wrens and
found that the wrens tended to have testosterone levels like those
found in breeding north-temperate male passerines but that male
honeyeaters had relatively low levels of Testosterone (T).
Investigators: Elizabeth Boliger and Terence Dawson, School of Biological Science, UNSW Sydney 2052.
Kangaroos are able to hop for many kilometres
at high speeds, and are thus considered to be highly athletic
animals. Their hopping locomotion is unique in its efficiency,
and has been well examined. However, the role of aerobic metabolism
at high speeds, over 25 km/h has yet to be determined. There are
no experimental data on the cardiovascular responses of exercising
kangaroos, and the capabilities of their hearts during intense
exercise is unknown. This study used wild animals at Fowlers Gap
Research Station to compared the size and the aerobic potential
of red kangaroo hearts (Macropus rufus) with that of the
hearts of a similarly sized placental, the feral goat (Capra
hircus).
Red kangaroos were found to have a heart to
body mass ratio 165% greater than that of feral goats, and 30
% larger than expected for marsupials of their size. Overall,
kangaroo hearts were found to have superior aerobic potential
to goat hearts, with a 70 % greater total mitochondrial volume.
The results suggest that red kangaroos have hearts capable of
high cardiac outputs during exercise, thus being able to deliver
large amounts of blood and oxygen per unit time to the working
muscles. The implication of these data is that, at times, the
muscles of red kangaroos have a much higher maximum oxygen demand
than those of goats. The athletic ability of kangaroos therefore
relies on both an energetically efficient locomotion and a relatively
high aerobic capacity.
 Return to index
Investigators: Kate J. Brown, Department
of Geography and Environmental Science, Monash University, Clayton
VIC 3168
Thesis Abstract:
This thesis reports on a study of hillslope
sediment transport in a small Australian arid zone catchment.
Primary data were derived from a network of 56 slope wash troughs,
representing one of the most extensive field sampling programmes
that has yet been employed in dryland geomorphic research. Supplementary
data were obtained using networks of erosion pins and analysis
of the radio-isotope caesium-137.
Trap masses and textural characteristics of
trough sediments were recorded at intervals during a five year
study period. To explore the controls on hillslope sediment transport
in the landscape, sediment trap masses and textural characteristics
were related to a suite of landscape features measured for the
area contributing sediment to each trough. Relationships between
landscape features and sediment transport were assessed using
bivariate correlation, multiple regression analysis and principal
components analysis. Results demonstrate a complex and variable
role for the individual landscape features. The statistical analyses
demonstrate that the order in which variables enter predictive
regression equations varies with rain event size and landscape
context. In addition, more landscape features contribute to the
explanation of variance during small rain events than during large
rain events. In large events, it is inferred that increasing volumes
of overland flow diminish the importance of some surface properties.
It is also demonstrated that sediment contributing areas are dynamic,
and that as a consequence sediment collection is best done with
unbounded sediment collection traps rather than bordered runoff
plots.
The findings of the study indicate that the
control of an individual landscape feature on hillslope sediment
transport is not as straight forward as first anticipated, and
that the influence varies according to the experimental technique
used, the size of the storm, the local gradient, and the way that
the trapped sediment is examined (for example, the sediment trap
mass or particle size).
A major contribution of this study is that
it provides one of the most comprehensive demonstrations of the
inter-linkages that exist between landscape features in complex
natural environments, and highlights the need to adopt multivariate
statistical techniques to explore the control of site characteristics
on sediment transport.
References
Brown K.J. 1997. An evaluation of the controls
on hillslope sediment transport in a small Australian arid zone
catchment: a case study from Homestead Creek catchment, western
New South Wales, Australia. Unpublished PhD thesis, Department
of Geography and Environmental Science, Monash University, 370pp.
Investigators: William A. Buttemer & Lee B. Astheimer
Depts. of Biological Sciences & Biomedical Sciences University
of Wollongong
We captured 24 adult male White-plumed Honeyeaters
from areas adjoining Fowler’s Gap and evaluated basal metabolic
rate (BMR) and morphological features before and 6-weeks after
subcutaneously implanting half of them with empty silastic capsules
(controls) and the other half with testosterone-filled capsules
(T-treated birds). There was no effect of testosterone on BMR,
body mass, adrenocortical sensitivity to capture stress, or blood
parasite load in these birds. However, T-treated males had significantly
higher haematocrits and maintained jet-black bills that typify
adult breeding males. In contrast, control males displayed a gradual
lightening of the proximal half of their bills, a colour change
never seen in free-living adult males at Fowler’s Gap, but
typical of non-breeding Fuscous Honeyeaters, a congeneric species
that breeds seasonally. We conclude that testosterone does not
directly increase energy expenditure in male White-plumed Honeyeaters,
but the T-induced rise in haematocrit may be beneficial to breeding
males in permitting higher aerobic capacity and more rapid recovery
following exhaustive activity.
Investigators: Terence J Dawson,
Cyntina Blaney, Adam Munn,
Andrew Krockenberger and Shane Maloney.
School of Biological Science, UNSW Sydney 2052.
While basic studies have been made on arid
zone kangaroos such as the red kangaroos (Macropus rufus ) (Dawson 1973), it is surprising that little is know about the
environmental physiology of the common mesic species such as the
eastern grey kangaroo (Macropus giganteus). This species
has a fossil history going back more than 5 million years, while
the red kangaroo appears to be a newly evolved species with a
fossil history restricted to the Pleistocene (Dawson 1995). It
has been assumed that many of the thermoregulatory characteristics
seen in arid zone species reflect adaptation to such harsh environments.
Eastern grey kangaroos have extended their range to the far west
reaching Fowlers Gap Research Station in the 1960s or early 1970s,
putatively due to the provision of more water sources for domestic
sheep. They are reported to drink more frequently than red kangaroos
in semi-arid habitats.
Red kangaroos have excellent thermoregulatory
abilities, using a sequence of evaporative heat loss mechanisms
to cope with external and internally produced heat loads. In regard
to the grey kangaroos little has been reported except that they
pant and lick. Licking has been suggested to be its major route
of evaporative heat loss at high temperatures. In this study we
compared the basic thermoregulatory features in the kangaroo species
which represent the two major evolutionary lineages of modern
kangaroos. We also explored the pattern of responses to high temperature
by these kangaroos. There were no major differences between the
species but numerous smaller but significant differences were
found. The heavier fur of grey kangaroos meant that heat loss
and therefore heat production was lower in the cold than in red
kangaroos. This would infer lower food requirements by the grey
kangaroo in winter. At high temperatures, an air temperature of
45°C, the red kangaroos appeared to be less stressed as measured
by their respiratory evaporative water loss. Panting however,
was the major heat loss mechanism of eastern grey kangaroos, but
red kangaroos maintained a lower body temperature with significantly
less respiratory water loss than seen in the grey kangaroos. This
would translate into a lower frequency of drinking as noted by
observations in Salon Paddock at Fowlers Gap.
Investigator: David Dunkerley
School of Geography and Environmental Science, Monash University,
Clayton, VIC 3168
Rainfall simulation over small experimental
runoff plots is being used as the main tool to research aspects
of the hydrologic and erosional response of landsurfaces within
the patterned chenopod shrublands that are widely developed in
the Fowlers Gap district. Various components of these landscapes
are being examined separately, including surfaces densely mantled
with gibbers, bare shrub interspace locations carrying cyanobacterial
crusts, and plots centred on bluebush shrubs. During the rainfall
simulation experiments, hydrologic response is assessed from surface
runoff rates monitored every 2 minutes; sediment samples are also
collected with this frequency. Soil loss is determined from the
turbidity of the runoff samples, using a calibrated relationship
with sediment mass.
The goal of this work is to build a comprehensive
understanding of surface and sub-surface characteristics that
influence hydrologic and erosional behaviour. This information
will be used in the development and testing of process-based models
seeking to account for the behaviour of patterned chenopod shrublands,
and to examine the potential impacts of disturbance and environmental
change on these landscapes.
As a part of this experimental program, the
role of surface conditions is being assessed systematically. Particular
attention has been paid to the role played by organic litter particles,
which cause varying degrees of water impoundment, and have the
potential to affect both hydrologic response and splash detachment
of sediment particles. Experiments have also focussed on the distinctive
hydrologic and erosional behaviour of plots containing shrubs.
In particular, the goal has been to separate those effects arising
in the plant canopy, such as the interception of raindrop kinetic
energy, from those arising in the soil surrounding the shrub,
such as organic matter and faunal effects.
The field program is supported by funding
from the Australian Research Council.
Publications:
Dunkerley D.L. 1997. Banded vegetation:development
under uniform rainfall from a simple cellular automaton model.
Plant Ecology 129: 103-111.
Dunkerley D.L. 1997. Banded vegetation: survival
under drought and grazing pressure based on a simple automaton
model. Journal of Arid Environments 35: 419-428.
Investigator:Rodger Kram1 and Terry Dawson2
1Dept of Integrative Biology, U C Berkeley, CA, USA.
2School of Biological Science, UNSW Sydney 2052
As a red kangaroo hops faster, the rate of
oxygen consumption (indicating metabolic energy) remains nearly
the same; almost all other animals show proportional increases
with speed. This phenomenon has been attributed to exceptional
elastic energy storage and recovery via long compliant leg tendons.
Compliant tendons may allow muscle fibers to act primarily as
economical tension generators. Kangaroo muscles may also be exceptionally
efficient. To determine if kangaroos have exceptionally efficient
muscles, we measured the metabolic cost of uphill hopping where
muscle fibers must perform mechanical work against gravity. We
found that uphill hopping was much more expensive than level hopping.
The maximal rate of oxygen consumption measured (3 ml O2 kg-1
s-1) exceeds all but a few vertebrate species. However, efficiency
values were normal, ~30%. Biomechanical measurements indicated
that the lack of increase in oxygen consumption at faster speeds
cannot be explained by an increase in the effective mechanical
advantage of the extensor muscles of the ankle joint. Our measurements
made in the USA at Harvard University and in Australia at Fowlers
Gap Research Station suggest that the preferred speeds of red
kangaroos may be determined by the acceptable levels of tendon
stress and not energetic cost and that near critical tendon stresses
occur at the speeds reported to be their maximum.
Investigators: Anja Naujeck1, David Croft2 and J.
Parzefall1
1 Institute of Zoology, University of Hamburg
2School of Biological Science, UNSW Sydney 2052
During a 4 ½ month stay on Fowlers Gap, investigations
on the food selection of Euros (Macropus robustus erubescens)
in different habitats were carried out. Earlier studies showed
that some male Euros moved between the flats, slopes and hills
whereas others always stayed near to the females in the slopes
or hills. These findings posed the question: why do male Euros
behave differently and what could be the benefit of the different
behaviours? Thus the aim of the present study was to get better
knowledge about possible factors influencing the habitat preferences
of the Euros. This involved a comparison of the structure and
vegetation composition of the different habitats, and of the foraging
behaviour of the animals.
During the study period observations were
made on seven radio collared male Euros as well as on some male
and female Euros without a collar. In general one observation
lasted about 40 min and was carried out in the early morning hours
or the evening. The social status (alone, with female, in a mating
group) was recorded as well as all behaviour including the number
of bites on different plant categories. To investigate the density
and composition of the vegetation, plants were classified into
different categories and the density was calculated by the ‘wandering
quarter method’.
The results showed that the habitats - flats,
slopes and hills - only differed in the density of the category
grass+forb but not in those of Saltbush, Bluebush and Copperburr.
The highest density for the category grass+forb was found in the
flats, the lowest in the hills. The observations showed that Euros
do select their food. Sometimes they ate plants like Lemon scented
grass or dried up wood, which are both an unusual foods. Lemon
scented grass has a high proportion of ethereal oil and dried
up twigs are non-digestible. It seemed that the animals knew about
these plants and chose them because of the secondary cell contents
or structures. The eating of Lemon scented grass or dried up wooden
twigs could therefore be explained by the health supporting character
of these plants and the activation of body functions.
The relationship between body size and foraging
behaviour was examined by the comparison of male and female Euros
in the same habitat. Due to their higher metabolic rate, female
Euros had a slightly higher rate of bites/min than males and they
ate higher proportions of easily digestible plants like forbs,
and sometimes Copperburr. The number of bites/min of male Euros
in the hills was a little lower than that of the other habitats
there were no significant differences between the three habitats.
Also the plants selected by the animals were the same in all three
habitats but the proportions differed. In habitats with a high
density of grasses male Euros preferred to eat these, but as grass
density declined they increased the proportion of Saltbush in
their diet. The foraging behaviour of Euros follows the principle
of energy maximisers. In areas with a declining grass density
it seemed that they adapted their behaviour optimally to their
environment. With a low density of grasses on the slopes and hills,
large male Euros may have difficulty in fulfilling their high
total energetic requirements. The movements of male Euros from
these areas to the flats could therefore be explained by the higher
grass density and energy supply present in the flats.
This study was too short to resolve the question
as to which strategy (remaining in the hills or moving between
the hills and flats) gives the higher fitness. Further long-term
study is required to determine whether is it more efficient to
forage optimally in the flats and to move only from time to time
to the slopes and hills to compete for mating opportunities, or
to stay near to the females and try to get every mating opportunity
at the cost of optimal foraging?
Investigators: Marc Robson1, Anthony Milne1 and Qiming Zhou2,
1School of Geography, UNSW, Sydney
2052
2Department of Geography, HKBU, Hong Kong SAR, China.
Shrub steppes occupy approximately 308,000
km2 of the Australian mainland. These communities are
generally composed of clumped woody perennial shrubs separated
by areas of bare ground. Following rain these bare areas become
covered by low annuals, grasses and forbs. The shrublands are
highly regarded by the pastoral industry and have been utilised
for the grazing of sheep and cattle since the 1850’s. Coincident
with the initiation of grazing practices, was large-scale land
degradation due primarily to overgrazing. Over time the community
structure of the shrublands was changed through the removal of
the perennial shrubs by stock, with subsequent erosion and replacement
by other species. This mismanagement resulted in a decline in
the carrying capacity of the rangelands, as large tracts of once
productive shrublands were replaced by unpalatable vegetation
and scalded surfaces.
In order to manage the rangelands in a sustainable
way it is important to maintain the cover of perennial shrubs,
as it is these plants which are primarily responsible for protecting
the soil from erosion. Perennial shrubs should be regarded by
the land manager as maintainers of landscape stability and secondarily
as a forage resource. The most crucial time for the manager is
in dry periods when all the preferred forage (forbs and grasses)
has been removed leaving only the shrubs to graze. Decisions must
be made, based on the state of the shrubs and soil condition,
as to when stock should be relocated. This three year project
is been undertaken with the aim of providing the land manager
with quantitative information concerning rangeland condition with
particular emphasis on the perennial shrub component.
Bladder Saltbush (Atriplex vesicaria)
was selected for this study because of its wide spread distribution
and sensitivity to grazing. This species is generally preferred
to other perennial shrubs as a source of forage when the more
palatable grasses and forbs have been eaten and as such, should
be carefully monitored to ensure its persistence during those
times in which it is being grazed. Remotely sensed satellite data
is particularly suited to this task as it can provide cost effective
and continuous information on rangeland condition at the scales
required by the pastoral industry. Problems remain however, to
relate the spectral reflectance measurements recorded by satellites
to quantitative surface variables such as cover and biomass.
This project will attempt to produce a methodology
which will allow for the extraction of quantitative surface variables
from satellite imagery. This information will be used to construct
a rangeland GIS which will aid the land manager in maintaining
the stability and therefore, the productivity of the land.
Investigators: Lisa Silva and David B. Croft
School of Biological Science, UNSW Sydney 2052
We examined nest site spacing and selection,
diet and parental care of the Wedge-tailed Eagle during the breeding
season (June-November) of 1997. The location of 40 nests was determined
using a GPS. The dispersion of these nests was analysed using
the method of Hopkins (1954) and the frequency distribution of
inter-nest distances was compared to a Poisson distribution. Nest
sites were aggregated rather than randomly dispersed across Fowlers
Gap suggesting habitat selection. Inter-nest distances between
0-5 km and 17-20 km were significantly over-represented relative
to a Poisson distribution. Thus nest-sites are aggregated but
each aggregation is some distance from another. A comparison of
nest trees to non-nest trees showed that tree and crown heights,
and crown sectional area were significantly higher and larger,
respectively, in nest trees situated near major tributaries and
creek beds than non-nest trees. In flat and ridge habitats unassociated
with creeklines, few differences were found between nest and non-nest
trees.
Time-lapse video recording was used to observe
behaviour and diet at nests during incubation and rearing of chicks.
The frequency and composition of prey items brought to the nest
was recorded from mid-September to early October at two nests,
one with a single chick and one with two chicks. The density of
lambs, young-at-foot (Yaf) macropods and rabbits was estimated
for areas around the nests. Rabbits were the most common prey
item, followed by bearded dragons. Only 5.7% of the prey were
Yaf and none were lambs even though lamb density was twice that
of Yaf. Bearded dragons seem to be staple for feeding chicks and
rabbits were a prominent diet item in spite of reduced abundance
from RCD. The frequency, duration and temporal variation of several
parental behaviours were recorded from both nests. Parental behaviour
decreased as the chicks matured, expect that arrival at the nest
with food increased with demand from the growing chicks. The pair
with two chicks invested less time in preening and brooding than
the pair with one chick. However, the two chicks were reared in
a very exposed nest and the inadequate crown cover increased the
parents’ investment in shading the chicks
The loss of crown cover in many trees (due
to drought and perhaps fire) and the need for adequate nest over
in arid regions may explain why Wedge-tailed Eagles build several
nests in different years. Likewise is may explain the irregularity
of nest spacing. Further research is needed on nest site selection
in relation to prey availability. The novel use of video proved
beneficial in gaining a more comprehensive record of behaviour
across time compared to direct observation. Furthermore, diet
was better characterised than analyses of prey remains at nest
since some items were carried away. However, care must be taken
in setting up and maintaining video equipment if inadvertent failure
of the clutch to hatch is to be avoided.
Investigators: Michaela Strätz1, David B. Croft2 and
Udo Gansloßer1
1Institute for Zoology, University of Erlangen-Nürnberg,
D-91058 Erlangen Germany
2School of Biological Science, UNSW Sydney 2052
Re-introduction of endangered species into
the wild is an attractive conservation tool. In Australia, many
wildlife welfare organisations rescue and release injured and
orphaned native species. These therefore provide models for captive
release programs even though many of the species, such as the
Red Kangaroo, are common in the wild. Thus we investigated the
feeding ecology and behaviour of re-introduced and free-ranging
wild Red Kangaroos in a short 4-month study at Fowlers Gap. One
prospective release candidate, a female, provided detailed information
on its foraging behaviour on natural pasture.
Individuals for release were held in a large
4-ha enclosure providing a period of acclimatisation and familiarity
with natural pasture before being turned loose. This is a so-called
‘soft release’ technique, which contrasts with ‘hard
release’ where the captive-reared individual has no period
of familiarisation. The value of soft release to future survival
in the wild has not been studied in Red Kangaroos and so the study
was guided by the need to gather information relevant to this
question. We therefore studied foraging behaviour, group size,
mobility and vigilance of wild, re-introduced and captive individuals.
We also mapped plant distribution and density using the Wandering
Quarter method (Catana 1963). The quality of plants was determined
as the product of greenness and height or diameter.
Free-ranging wild and re-introduced kangaroos
foraged in areas of similar plant composition and quality. The
re-introduced females were most often alone or with their young-at-foot
whereas wild females were in a median group size of four. However,
females with young-at-foot are often distant from other individuals
in red kangaroo populations. Furthermore group size varied with
grass density and patch size. Thus re-introduced females may not
integrate into the wild population but this needs much further
study. Both re-introduced and wild subjects spent the same amount
of time feeding around dawn and dusk and did not differ in other
aspects of their time/activity budgets except that the re-introduced
individuals sniffed and were more vigilant than their wild counterparts.
Differences in vigilance could be explained by smaller group sizes
in the re-introduced individuals.
Hand-reared Red Kangaroos which are liberated
back into the wild through a ‘soft-release’ program
seem to adapt to their new conditions. They forage in similar
quality areas and with similar efficiencies to their wild counterparts.
However, long-term studies are required to determine whether survival
equates to reproductive success comparable to their mother-reared
peers. Observations on the female (and others) in the enclosure
suggest she is an inattentive mother and here offspring would
be at considerable risk outside the protection of a fence.
Investigators: W. T. Tay1,2 & R. H. Crozier1
1Department of Biochemistry and Genetics, La Trobe University,
Bundoora 3083, Australia
2Department of Ecology and Systematics, P.O. Box 17,
Fin-00014 University of Helsinki, Finland.
Rhytidoponera sp. 12 is a queenless
ponerine ant species commonly found in the semi-arid zones of
Australia. Within individual R. sp. 12 colonies there existed
multiple workers that were mated (Crozier et al. 1984) known as
gamergates (Peeters and Crewe 1984). Based on allozyme studies
of the average worker relatedness in the population, cohabiting
gamergates were inferred to be either weakly related or unrelated
(Crozier et al. 1984). Furthermore, limited information was available
regarding the mating behaviour and colony founding strategy of R. sp. 12 due to the remoteness of their habitats. Recently
microsatellite markers were developed for R. sp. 12 (W.
T. Tay unpublished thesis) and could be used to provide essential
genetic information leading to a better understanding of R.
sp. 12 sociogenetic organisation.
To further understand how coexisting gamergates
were related, five R. sp. 12 colonies with known intracolony
worker relatedness (W. T. Tay unpublished data) located in the
Conservation Paddock were excavated. Intracolony gamergate relatedness
was estimated directly from gamergates that have been identified
and confirmed by dissection (ie, gamergates have sperm-filled
spermathecae). The sperm samples collected from these gamergates’
spermathecae provided opportunities to estimate the mating frequencies
of both gamergates and their mating partners. Our results
from mating behaviour study, gamergate and male mate relatedness
analyses suggested the following life-history traits in R.
sp. 12:
- Workers mated near the colony entrance
or within the colony.
- Newly mated workers were accepted back
into their parental colonies.
- The male mating-partners originated from
neighbouring colonies and were probably attracted to receptive
workers though the workers releasing male-attracting pheromones.
- Establishment of new colonies (established
with the help from a group of unmated workers) probably involved
individual gamergates and/or groups of related or full sister
gamergates.
- Gamergates and males generally mated only
once although low frequencies of multiple mating were detected
in both males and gamergates.
- Within individual colonies cohabiting (sister)
gamergates sometimes mated with the same males leading to highly
related worker offspring.
References
Crozier RH, Pamilo P, Crozier YC (1984) Relatedness
and microgeographic genetic variation in Rhytidoponera mayri,
an Australian arid-zone ant. Behavioral Ecology and Sociobiology
15:143-150.
Peeters C, Crewe R (1984) Insemination controls
the reproductive division of labour in a ponerine ant. Naturwissenschaften
71:50-51.
Tay WT (1998) Worker migration, mating behaviour
and sociogenetic organisation of Rhytidoponera sp. 12 (Formicidae:
Ponerinae). Ph. D. Thesis, La Trobe University, Melbourne. x +
89 pp
Investigators: Ariane Thiess1, David B. Croft2 and
Udo Gansloßer3
1Institute for Zoology, University of Hamburg, Germany
2School of Biological Science, UNSW Sydney 2052
3Institute for Zoology, University of Erlangen-Nürnberg,
D-91058 Erlangen Germany
Four species of free-ranging female kangaroos
with young-at-foot were observed and their alarm and flight behaviour
was compared. The species were the Red Kangaroo (Macropus rufus),
the Western Grey Kangaroo (M. fuliginosus), the Eastern
Grey Kangaroo (M. giganteus) and the Euro (M. robustus
erubescens). Since young-at-foot live under a great risk of
predation and are still dependent on milk provision by their mothers,
it is important for their survival to stay in close proximity
to their mothers. So in dangerous situations mother and young
have to cooperate in a way, that the young will not get lost.
Until this study was conducted, it was unsure, if the species
observed behaved in a different way concerning the mother-young
cooperation during alarm and flight behaviour.
The aim of this study was, to find out:
- how mother and young cooperate during alarm
and flight behaviour,
- which kind of anti-predator behaviour is
shown by the different species, and
- whether there are distinctions between
the species.
During the observations AT approached the
animals by foot and noted their responses to her as a model-predator.
Different activities, which possibly give insight into the cooperation
behaviour, were recorded and assessed. Relatively few observations
were obtained for the Eastern Grey Kangaroos and the Euros, and
so it was only possible to compare the Red Kangaroos with the
Western Grey Kangaroos in detail.
Mothers of Red and Western Grey Kangaroos
looked first at the observer, started flight first, determined
the direction of flight and showed flight intention movements
more often than their young. In the other two species these differences
between mother and young-at-foot were, with one exception, not
found. The reason may be partly the low numbers of observations
in Eastern Grey Kangaroos and Euros. Euro mothers started like
Red and Western Grey Kangaroos more often for flight than their
young. In all of the four species, neither the mother nor the
young hopped more often in front of the other one or followed
it, respectively. Comparisons between the species only revealed
a distinction in the intention movement of Western Grey and Red
Kangaroos. In all other activities the mother-young cooperation
was not different between the species.
While investigating the anti-predator behaviour,
alert distances, flight distances, flight length, flight duration,
flight speed, habitat type at the end of flight and the distances
between kangaroos and observer before and after flight were recorded.
The species’ reaction varied in the alert distance and the
choice of the habitat type at the end of their flight. Red Kangaroos
and Western Grey Kangaroos were already alert at greater distances
than the Eastern Grey Kangaroos. Red kangaroos chose open areas
to end the flight, whereas Western Grey Kangaroos hid for the
most part in high thickets at the end of their flight.
How far the differences in some behaviours
between Eastern Grey Kangaroos and the other kangaroo species
are related to different habitats or in species-specific behaviour,
could not be clarified due to the lack of more observations on
Eastern Grey Kangaroos in our study. As there were only few differences
found in the behaviour of Red Kangaroos and Western Grey Kangaroos,
mothers with young-at-foot of these two species probably do not
have fundamentally different anti-predator strategies.
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