Short-term gland secretion in the African elephant: tourist disturbance or social interactions as source for secretion?

The temporal gland is an organ found exclusively in elephants, located midway between the eye and the ear. Hypotheses exist about what factors lead to the release of the secretion but so far few studies have taken place in the wild, especially of secretion in relation to behaviour. It has been suggested that the secretion serves in communication or that it is a symptom of stress. These hypotheses were tested by observing free-ranging elephants in Etosha National Park, Namibia. Factors considered were the impact of carnivores, of herds of other herbivores, of vehicles and of other elephants on the amount of secretion in focal elephant families. Neither other mammals nor tourists, recorded in terms of vehicles, seemed to affect secretion, but the secretion increased with the rate at which members of elephant families displaced each other. It is concluded that the secretion is predominantly related to social behaviour and less to factors extrinsic to the elephant herd.     

Is there a future for elephants in West Africa?

The elephants of West Africa have experienced a long history of human disturbance. Before 1800 they were much affected by the precolonial empires of the savanna and Sahelian zones, the trans-Saharan trade routes, and the coastal trade established by the Europeans. During the 19th century, the increasing demand for ivory from Europe and North America, the European penetration of the region, and the evolution of breech-loading rifles devastated the remaining elephants. The elephant population of West Africa collapsed before the outbreak of World War I because of intense hunting for ivory. This collapse pre-empted the decline that would have occurred anyway due to the rapid growth of the human population and consequent loss of habitat. Elephants now find themselves in about 70 small isolated populations that cover only 5% of the region. These fragments are very vulnerable – whether in the arid lands or the humid forests – to poaching and general human disturbance. There are few data on numbers; most of the population estimates are guesses. Two-thirds of the populations are thought to consist of fewer than 200 animals and therefore have a low probability of surviving the next century. As more habitat is lost to human activities, West African elephants will soon remain only in protected areas. But many parks and reserves are managed poorly and cannot offer effective protection; they do not guarantee a future for elephants. In addition, their crop-raiding habit makes elephants unpopular in rural communities surrounding protected areas. Human populations are expected to continue growing and resources for conservation are scarce. The future of West African elephants lies in a small network of well-protected areas.     

Population viability analysis for Guarianthe aurantiaca, an ornamental epiphytic orchid harvested in Southeast México

The trade of wild epiphytic orchids has put many populations at risk of extinction; however, little is known about the impact of repeated harvesting of individuals on population dynamics. A population viability analysis (PVA) was developed to simulate the impact of harvesting on the risk of extinction of a population of an epiphytic orchid that is sold in Mexican markets. In January 2004, 388 individuals of Guarianthe aurantiaca were labeled and measured. The same individuals were measured again in December 2005 and December 2006. Capsule production and mortality were also recorded. Deterministic (d) and stochastic (s) matrix models were developed to estimate the population growth rate (λ). A PVA was developed to evaluate the probability of extinction over a 100-year period, given a threshold of 5% of the initial population and different harvest intensities of G. aurantiaca . The λ_d values were statistically indistinguishable from unity (0.989 ± 0.103 for 2004–2005; 0.990 ± 0.087 for 2005–2006); the λ_s values were below unity (0.988 ± 0.001). The reproductive stages had the highest elasticity values, whereas the persistence of individuals in their category was the demographic process with the highest elasticity. A life table response experiment showed that the difference in the λ_d values was accounted for by the positive contribution of the stasis of individuals in category j and the retrogression of individuals in category r₁ to category j. The extinction risk was 100% when more than 5% of the reproductive individuals were harvested. The results suggest that this G. aurantiaca population is in a precarious equilibrium and harvesting should be controlled and restricted to immature individuals.     

An Elephant in the Room: Okavango Safari Hunting as Ecotourism?

Safari hunters’ acute awareness of the widely held negative perceptions of their practice has led to their development of strong justifications and defensive assertions in favour of hunting. Far from being a primarily destructive practice, they claim that safari hunting in the Okavango Delta, Botswana, can be seen as an exemplary form of ecotourism, which benefits local communities, facilitates environmental conservation and provides the ultimate nature experience for participants. While research supports their claims to an extent, the ethical quandaries evinced by hunters themselves, the complex dialectic between local and global controls, and the elite, racialised and gendered nature of hunting speaks to a more complex and conflicted situation.     

种群生存力分析（PVA）的方法与应用

随着人们对资源的加速利用,生境丧失和破碎化导致物种濒危问题日益严重.以岛屿生物地理学为理论起源的种群生存力分析（PVA）,通过分析和模拟种群动态过程并建立灭绝概率与种群数量之间的关系,为濒危物种保护提供了重要的理论依据和研究途径.在过去的几十年中,种群生存力分析已成为保护生物学中一项重要的研究内容.目前种群生存力分析发展稳定,但对其实际预测能力和准确性尚存质疑,应用方面也有待进一步发展.种群生存力分析的进一步完善还需要在理论和方法上的创新,特别是籍于景观生态学和可持续性科学的理念,将空间分析手段、经济社会因素纳入到物种和种群的预测和管理上,从而使其具有更完整的理论基础和更高的实用价值.为此,本文对种群生存力分析的历史、基本概念、研究方法、模型应用和准确性进行了综述,并提出了有关的研究展望.     

A TECHNIQUE TO ‘TAG’ SPECIFIC VOCALIZATIONS IN TAPE-RECORDINGS OF COMPLEX VOCAL INTERACTIONS

ABSTRACT

It has been suggested that African savanna elephants Loxodonta africana produce 31 different call types (Langbauer 2000). Various researchers have described these calls by associating them with specific behavioural contexts. More recently Leong et al. (2003) have attempted to classify elephant call types based on their physical properties. They classified 8 acoustically distinct call types from a population of captive elephants. This study focuses on one of these call types, the rumble, in a wild population of elephants in Kruger National Park, South Africa. A single family group of elephants was followed to record group behaviours and vocalizations from January through August 2001. By measuring the physical properties of 663 rumbles and subjecting these to cluster analysis, we present evidence that shows that rumbles can be categorized by their physical properties and that the resulting rumble types are associated with specific group behaviours. We characterize three types of rumbles that differ significantly by ten acoustic parameters. Two rumble types were associated with the elephant group feeding and resting, while the third was associated with socializing and agitation.     

长江江豚种群生存力分析

长江江豚是一个独立的种群,由于人类活动的影响,其数量呈下降的趋势,运用漩涡模型（ＶＯＲＴＥＸ７．３）分析了长江江豚的种群生存力,预测了未来１００ａ长江江豚的种群动态,比较了在假设环境条件下以及采取和不采取保护措施长江江豚种群的濒危程度,并模拟了江豚饲养群体的动态,主要结果显示,长江江豚在未来１００ａ内灭绝的概率为０．０１平均灭绝时间为１００ａ,如长江环境状况进一步恶化,长江江豚的灭绝概率针大幅度提