Individual preferences for sound tool design in a parrot

The rarity of tool manufacture in wild parrots is surprising because they share key life-history traits with advanced tool-using species, including large brains, complex sociality and prolonged parental care. When it does occur, tool manufacture in parrots tends to be innovative, spontaneous and individually variable, but most cases have been in captivity. In the wild, only palm cockatoos (Probosciger aterrimus) have been observed using tools regularly. However, they are unusual because they use tools to enhance their displays rather than for foraging or self-maintenance. Males in northern Australia make two types of tool from sticks and seed pods, which they tap rhythmically against a tree during display. We analysed 256 sound tools retrieved from 70 display trees. Drumsticks (89% of tools) were used more often than seed pod tools; most males manufactured only drumsticks, but some made both types. Individual males differed significantly in the design of their drumsticks including the length, width and mass but we found no evidence that neighbours copied each other. We discuss the highly individualized preferences for sound tool design in context of the behavioural predispositions behind the rarity of tool manufacture in wild parrots.

Can an introduced predator select for adaptive sex allocation?

Most species produce equal numbers of sons and daughters, and sex differences in survival after parental care do not usually affect this pattern. Temporary overproduction of the scarcer sex can be adaptive when generations overlap, the sexes differ in life-history expectations, and parents can anticipate future mating opportunities. However, an alternative strategy of maximizing the competitiveness of the more abundant sex in these circumstances remains unexplored. We develop theory showing how mothers can maximize reproductive value when future mate competition will be high by producing more sons in the advantageous early hatching positions within their broods. Our model for optimal birth order was supported by long-term data of offspring sex in a parrot facing catastrophic female mortality caused by introduced predators. Swift parrots (Lathamus discolor) suffer high female mortality due to introduced sugar gliders (Petaurus breviceps) creating fluctuating male-biased adult sex ratios. Offspring hatched early within broods fledged in better condition, and in support of our model were more likely to be male in years with higher adult female mortality. We found a highly significant rank-order correlation between observed and predicted birth sex ratios. Our study shows the potential for mothers to maximize reproductive value via strategic biases in offspring sex depending on the advantages conferred by birth order and the predictability of future mate competition. Our long-term data support the predictions and appear to suggest that sex allocation strategies may evolve surprisingly quickly when anthropogenic pressures on populations are severe.

The trajectory of dispersal research in conservation biology. Systematic review

Dispersal knowledge is essential for conservation management, and demand is growing. But are we accumulating dispersal knowledge at a pace that can meet the demand? To answer this question we tested for changes in dispersal data collection and use over time. Our systematic review of 655 conservation-related publications compared five topics: climate change, habitat restoration, population viability analysis, land planning (systematic conservation planning) and invasive species. We analysed temporal changes in the: (i) questions asked by dispersal-related research; (ii) methods used to study dispersal; (iii) the quality of dispersal data; (iv) extent that dispersal knowledge is lacking, and; (v) likely consequences of limited dispersal knowledge. Research questions have changed little over time; the same problems examined in the 1990s are still being addressed. The most common methods used to study dispersal were occupancy data, expert opinion and modelling, which often provided indirect, low quality information about dispersal. Although use of genetics for estimating dispersal has increased, new ecological and genetic methods for measuring dispersal are not yet widely adopted. Almost half of the papers identified knowledge gaps related to dispersal. Limited dispersal knowledge often made it impossible to discover ecological processes or compromised conservation outcomes. The quality of dispersal data used in climate change research has increased since the 1990s. In comparison, restoration ecology inadequately addresses large-scale process, whilst the gap between knowledge accumulation and growth in applications may be increasing in land planning. To overcome apparent stagnation in collection and use of dispersal knowledge, researchers need to: (i) improve the quality of available data using new approaches; (ii) understand the complementarities of different methods and; (iii) define the value of different kinds of dispersal information for supporting management decisions. Ambitious, multi-disciplinary research programs studying many species are critical for advancing dispersal research.

Mind the sustainability gap

Despite increasing efforts to reach sustainability, key global biophysical indicators such as climate change and biodiversity loss continue to deteriorate rather than improve. Ongoing failure to move towards sustainability calls into question the focus of current research and policy. We recommend two strategies for progress. First, sustainability must be conceptualized as a hierarchy of considerations, with the biophysical limits of the Earth setting the ultimate boundaries within which social and economic goals must be achieved. Second, transdisciplinary research programs must confront key normative questions facing modern consumer societies. The humanities should have a key role in such programs. Assisted by these strategies, ambitious targets that realistically reflect the biophysical limits of the life-support system of the Earth must be set and relentlessly worked towards.

Cryptic gentes revealed in pallid cuckoos Cuculus pallidus using reflectance spectrophotometry

Many cuckoo species lay eggs that match those of their hosts, which can significantly reduce rejection of their eggs by the host species. However, egg mimicry is problematic for generalist cuckoos that parasitize several host species with different egg types. Some generalist cuckoos have overcome this problem by evolving several host-specific races (gentes), each with its own, host-specific egg type. It is unknown how generalist cuckoos lacking gentes are able to avoid egg rejection by hosts. Here we use reflectance spectrophotometry (300-700 nm) on museum egg collections to test for host-specific egg types in an Australian generalist cuckoo reported to have a single egg type. We show that the colour of pallid cuckoo (Cuculus pallidus) eggs differed between four host species, and that their eggs closely mimicked the eggs of the host they parasitized. These results reveal that pallid cuckoos have host-specific egg types that have not been detected by human observation, and indicate that gentes could be more common than previously realized.

Availability of nest hollows and breeding population size of eclectus parrots, Eclectus roratus, on Cape York Peninsula, Australia

The distribution of the Australian mainland endemic subspecies of the eclectus parrot, Eclectus roratus macgillivrayi, is currently confined to the lowland rainforests of the Iron–McIlwraith Ranges of eastern Cape York Peninsula. Females breed in large hollows in emergent rainforest trees that are readily visible from above. Aerial surveys were used to sample 58% of the rainforest (454 km2) of the Iron Range region to estimate the density of these nest trees. Corrections for overcounting bias (not all observed emergent trees were active nest trees) and undercounting bias (not all active nest trees were visible from the air) were made by ground-truthing over 70 trees. The tree count data were treated in two different ways, producing estimates of 417 (s.e. = 25) and 462 (s.e. = 31) nest trees for the Iron Range region. Long-term observational data on the number of eclectus parrots associated with each nest tree were used to estimate the population size of eclectus parrots at Iron Range: 538–596 breeding females, and 1059–1173 males. These results have three implications. First, this relatively low population estimate suggests that the Australian subspecies of eclectus parrots should be considered vulnerable to habitat loss or perturbation, especially in light of their complex social system, male-biased adult sex ratio, low breeding success and high variance in reproductive success among females. Second, the low density of nest trees suggests that eclectus parrots are absent from the rainforests of Lockerbie Scrub and the Jardine dunefields because these areas are too small. Finally, if eclectus parrots persisted in the Iron–McIlwraith region during the rainforest contractions of Pleistocene glacial maxima (e.g. 14 000–17 000 years ago), the refugium in this region must have been fairly substantial in order to support a viable population – probably larger than previously assumed.

Coalitions of relatives and reproductive skew in cooperatively breeding white-winged choughs

We used DNA fingerprinting to examine reproductive skew in cooperatively breeding white-winged choughs, Corcorax melanorhamphos, which live in groups of up to 20 individuals. Before a severe drought, groups that had been stable for multiple years were characterized by long-term monogamy involving a single breeding pair (high skew). After the drought, new groups formed from the amalgamation of multiple individuals and coalitions of relatives. At most one member of each faction succeeded in breeding, such that skew was dependent on the number of unrelated factions, and not group size. In the new groups, dominant males and females with supporting relatives were always successful. Whereas most females without support also gained breeding positions, many males without family support failed to breed. Thus subordinates gain indirect fitness by first helping related males to secure a breeding position, and then helping to raise their young. Our study demonstrates the advantage of operating in coalitions, and suggests that the acquisition of future allies may be a major benefit of helping behaviour in this species.

The cost of helping

Cooperative breeding in mammals, birds and fish has provided evolutionary biologists with a rich framework for studying the causes and consequences of group-based reproduction. Helping behaviour is especially enigmatic because it often entails an individual sacrificing personal reproduction while assisting others in their breeding attempts. The decision to help others to reproduce is affected by immediate and future costs analogous to those of direct reproduction, but these components of the equation have usually been neglected. Recent research suggests that the type of benefit sought could determine the extent of help given.

Group territoriality in two populations of African lions

Lionesses, Panthera leoin the Serengeti ecosystem, Tanzania, assess the odds of winning group-territorial contests by counting the number of opponents they hear roaring. They will approach intruders aggressively only if they outnumber them. Here the lionesses in the Serengeti are compared with another population living nearby but in strikingly different ecological circumstances. The lions of Ngorongoro Crater live at much higher densities owing to year-round availability of non-migratory prey species, but also suffer higher mortality from fighting. Playback experiments showed that lionesses in the crater differ from those in the Serengeti by approaching 'intruders' more quickly when the odds of winning are low. This increased aggression is interpreted in terms of the greater difficulty of holding a territory at high population density.

Development of cooperative territoriality in juvenile lions

African lions, Panthera leo, engage in many cooperative activities including hunting, care of young, and group territoriality, but the contribution of juvenile lions to these activities has never been documented. Here we present experimental evidence that juvenile lionesses make a gradual transition to group-territorial defence between weaning (8 months) and sexual maturity (42 months). When challenged by simulated intruders played from a loud-speaker, juvenile females (but not males) become progressively more likely to join the adult females in territorial defence with age, and their behaviour is affected by both the number of defending adults and the number of intruders. We interpret the ability of juveniles to assess relative numbers as an adaptation for assessing the risk of territorial conflict according to their own fighting ability, and the ability of their pride of successfully defend the territory. The difference between the sexes reflects the greater value of the natal territory to philopatric females. Adult females display a variety of strategies when defending the territory, including unconditional and conditional forms of cooperation. We show here that individuals display the rudiments of these strategies as juveniles.

Complex cooperative strategies in group-territorial African lions

Female lions (Panthera leo) showed persistent individual differences in the extent to which they participated in group-territorial conflict. When intergroup encounters were simulated by playback of aggressive vocalizations, some individuals consistently led the approach to the recorded intruder, whereas others lagged behind and avoided the risks of fighting. The lead females recognized that certain companions were laggards but failed to punish them, which suggests that cooperation is not maintained by reciprocity. Modification of the "odds" in these encounters revealed that some females joined the group response when they were most needed, whereas other lagged even farther behind. The complexity of these responses emphasizes the great diversity of individual behavior in this species and the inadequacy of current theory to explain cooperation in large groups.

Computer-aided hybridoma screening. Production of monoclonal antibodies against membrane fractions from mammary tumour tissue

Monoclonal antibodies were raised against membrane fractions from mammary tumour tissue. 746 hybridomas were obtained against the so-called membrane fraction '2a' and 1393 hybridomas against the so-called 'top-region'. These hybridomas were tested with an immunodot assay, cell-binding radioimmunoassay and an immunocytological screening assay using several antigens. In the evaluation of these data we used the common database software (dBASE II) on a personal computer. To facilitate computer handling, even for the non-specialist, we programmed our individual menu-driven software for computer-aided hybridoma screening.