Effects of social disruption in elephants persist decades after culling.

BACKGROUND Multi-level fission-fusion societies, characteristic of a number of large brained mammal species including some primates, cetaceans and elephants, are among the most complex and cognitively demanding animal social systems. Many free-ranging populations of these highly social mammals already face severe human disturbance, which is set to accelerate with projected anthropogenic environmental change. Despite this, our understanding of how such disruption affects core aspects of social functioning is still very limited. RESULTS We now use novel playback experiments to assess decision-making abilities integral to operating successfully within complex societies, and provide the first systematic evidence that fundamental social skills may be significantly impaired by anthropogenic disruption. African elephants (Loxodonta africana) that had experienced separation from family members and translocation during culling operations decades previously performed poorly on systematic tests of their social knowledge, failing to distinguish between callers on the basis of social familiarity. Moreover, elephants from the disrupted population showed no evidence of discriminating between callers when age-related cues simulated individuals on an increasing scale of social dominance, in sharp contrast to the undisturbed population where this core social ability was well developed. CONCLUSIONS Key decision-making abilities that are fundamental to living in complex societies could be significantly altered in the long-term through exposure to severely disruptive events (e.g. culling and translocation). There is an assumption that wildlife responds to increasing pressure from human societies only in terms of demography, however our study demonstrates that the effects may be considerably more pervasive. These findings highlight the potential long-term negative consequences of acute social disruption in cognitively advanced species that live in close-knit kin-based societies, and alter our perspective on the health and functioning of populations that have been subjected to anthropogenic disturbance

Degenerate Quantum Codes for Pauli Channels

A striking feature of quantum error correcting codes is that they can sometimes be used to correct more errors than they can uniquely identify. Such degenerate codes have long been known, but have remained poorly understood. We provide a heuristic for designing degenerate quantum codes for high noise rates, which is applied to generate codes that can be used to communicate over almost any Pauli channel at rates that are impossible for a nondegenerate code. The gap between nondegenerate and degenerate code performance is quite large, in contrast to the tiny magnitude of the only previous demonstration of this effect. We also identify a channel for which none of our codes outperform the best nondegenerate code and show that it is nevertheless quite unlike any channel for which nondegenerate codes are known to be optimal.Comment: Introduction changed to give more motivation and background. Figure 1 replace

Entanglement can completely defeat quantum noise

We describe two quantum channels that individually cannot send any information, even classical, without some chance of decoding error. But together a single use of each channel can send quantum information perfectly reliably. This proves that the zero-error classical capacity exhibits superactivation, the extreme form of the superadditivity phenomenon in which entangled inputs allow communication over zero capacity channels. But our result is stronger still, as it even allows zero-error quantum communication when the two channels are combined. Thus our result shows a new remarkable way in which entanglement across two systems can be used to resist noise, in this case perfectly. We also show a new form of superactivation by entanglement shared between sender and receiver.Comment: 4 pages, 1 figur

The effects of sexual dimorphism on the movements and foraging ecology of the African elephant.

Thesis (Ph.D.)-University of KwaZulu-Natal, 2005.Large herbivores are key components of terrestrial biomes because of their relative abundance and pronounced influence on ecosystem functioning and habitat structure. To manage and conserve these species effectively, requires greater understanding of their distribution and use of resources at varying spatial and temporal scales. Sexual dimorphism is one aspect of large herbivore ecology likely to have a significant effect on resource use and community level interactions. Elephants present an ideal species to test the influence of sexual dimorphism due to their marked body size and pronounced behavioural differences. This study used location and behavioural data collected over an 8 year period in five different South African reserves, all of which had well documented elephant populations. The reserves were relatively small (<1000 km2) and had augmented water supplies so analyses were not influenced by surface water availability. Results indicated that male and female elephants resolve their available range at distinctly different scales. Both sexes were shown to expand their ranges with increasing forage quality, however males were the most flexible in their temporal and spatial response during periods of low resource availability. Females were more selective than males, targeting higher quality forage and being less destructive in their feeding approach. This may be due to females' higher mass specific energy requirements associated with their smaller body size and substantial reproductive investment. They were also constrained by the costs of group living compared to male elephants which range independently. Sexual segregation is a consequence of body size dimorphism and was investigated at both the habitat and plant scale to elucidate the mechanism driving the separation of the sexes. Whilst individual habitat preferences exist, these are not sufficient to segregate the sexes. At the plant scale, significant differences were shown with regard to foraging duration, tree size and plant parts eaten. Further investigation of sexual segregation involved testing the recently proposed activity budget hypothesis. Males and females have similar daily activity budgets and relatively high levels of behavioural synchrony, which is not sufficient to explain segregation. Instead, the marked sexual segregation appeared to be caused by social organisation, reproductive strategies and the divergent foraging behaviour of males and females at the plant scale. This research highlights the importance of considering male and female dimorphic herbivores as ecologically distinct species. For example, male elephants are likely to be driving the majority of destructive foraging bouts and this will often be in a heterogeneous manner, especially during periods of resource scarcity. Therefore, the effective management of elephants requires considering population structure, individual behaviour and population size

The effects of sexual dimorphism on the movements and foraging ecology of the African elephant

Abstract available on PDF file

Can non-private channels transmit quantum information?

We study the power of quantum channels with little or no capacity for private communication. Because privacy is a necessary condition for quantum communication, one might expect that such channels would be of little use for transmitting quantum states. Nevertheless, we find strong evidence that there are pairs of such channels that, when used together, can transmit far more quantum information than the sum of their individual private capacities. Because quantum transmissions are necessarily private, this would imply a large violation of additivity for the private capacity. Specifically, we present channels which display either (1) A large joint quantum capacity but very small individual private capacities or (2) a severe violation of additivity for the Holevo information.Comment: We both think so. 4 pages and 3 figures explain wh