Elephant Loxodonta Africana Population Research Articles

Seasonal and spatial vulnerability to agricultural damage by elephants in the western Serengeti, Tanzania

AbstractIn the western Serengeti of Tanzania, African elephant Loxodonta africana populations are increasing, which is rare across the species’ range. Here, conservation objectives come into conflict with competing interests such as agriculture. Elephants regularly damage crops, which threatens livelihoods and undermines local support for conservation. For damage reduction efforts to be successful, limited resources must be used efficiently and strategies for mitigation and prevention should be informed by an understanding of the spatial and temporal distribution of crop damage. We assessed historical records of crop damage by elephants to describe the dynamics and context of damage in the western Serengeti. We used binary data and generalized additive models to predict the probability of crop damage at the village level in relation to landscape features and metrics of human disturbance. During 2012–2014 there were 3,380 reports of crop damage by elephants submitted to authorities in 42 villages. Damage was concentrated in villages adjacent to a reserve boundary and peaked during periods of crop maturity and harvest. The village-level probability of crop damage was negatively associated with distance from a reserve, positively with length of the boundary shared with a reserve, and peaked at moderate levels of indicators of human presence. Spatially aggregated historical records can provide protected area managers and regional government agencies with important insights into the distribution of conflict across the landscape and between seasons, and can guide efforts to optimize resource allocation and future land use planning efforts.

Resource selection and landscape change reveal mechanisms suppressing population recovery for the world's most endangered antelope

Summary Understanding how bottom‐up and top‐down forces affect resource selection can inform restoration efforts. With a global population size of <500 individuals, the hirola Beatragus hunteri is the world's most endangered antelope, with a declining population since the 1970s. While the underlying mechanisms are unclear, some combination of habitat loss and predation are thought to be responsible for low abundances of contemporary populations. Efforts to conserve hirola are hindered by a lack of understanding as to why population density remains low, despite eradication of the viral disease, rinderpest. To elucidate factors underlying chronically low numbers, we examined resource selection and landscape change within the hirola's native range. Because hirola are grazers, we hypothesized that the availability of open areas would be linked both to forage and safety from predators. We quantified: (i) changes in tree cover across the hirola's historical range in eastern Kenya over the past 27 years; (ii) how tree cover has influenced resource selection by hirola; and (iii) interactions between tree cover and predation. Between 1985 and 2012, tree cover increased by 251% across the historical range of hirola. Tree encroachment was associated with a 98% decline of hirola and elephant Loxodonta africana populations, a 74% decline in cattle Bos indicus, an increase in browsing livestock by 327%, and a reduction in rainfall. Although hirola avoided tree cover, we found no evidence that predation on hirola increased with increasing tree cover. Synthesis and applications. Hirola may qualify as a refugee species, in which contemporary populations are restricted to suboptimal habitat and exhibit low survival, reproduction or both. The extinction of hirola would be the first of a mammalian genus on the African continent in modern history. We conclude that contemporary low numbers of hirola are due at least partly to habitat loss via tree encroachment, triggered by some combination of elephant extirpation, overgrazing, drought and perhaps fire suppression. We recommend a combination of rangeland restoration efforts (including conservation of elephants, manual clearing of trees, and grass seeding), increased enforcement of an existing protected area (Arawale National Reserve), and reintroductions to enhance recovery for this endangered species. These efforts will rely on enhanced support from the international conservation community and the cooperation of pastoralist communities with which the hirola coexist.

Elephant poaching in Niassa Reserve, Mozambique: population impact revealed by combined survey trends for live elephants and carcasses

AbstractTrends in the populations of large herbivores in Niassa Reserve, Mozambique, have been monitored through biennial aerial surveys since 1998. The elephant Loxodonta africana population has been subjected to intensive illegal hunting since 2006. We used a simple population model to mimic the observed trends in the numbers of live and dead elephants to demonstrate the impact of poaching. The number of fresh or recent carcasses recorded was used in the model as an index of the annual mortality rate. A maximum likelihood analysis to compare population models revealed that the best fit to the survey estimates of both live elephants and old or very old carcasses was a model that started with 6,635 elephants in 1987. This number increased through births by 4.6% annually and decreased through deaths from natural and anthropogenic causes. In the best-fit model, the mean mortality rate in any year was 3.2 times the observed 1 + 2 carcass ratio (ratio for carcasses in age categories 1 and 2), and carcasses remained visible for a mean of 6 years. The model suggested that c. 900 elephants were poached during 2007–2010 and another c. 1,000 during 2011. Population estimates for live elephants and carcasses are now routine outcomes of aerial surveys conducted as part of the CITES programme for Monitoring the Illegal Killing of Elephants, and our method can be applied to any population with a time series of estimates for live and dead elephants.

A review of historical trends in the distribution and abundance of elephants Loxodonta africana in Mozambique

The elephant Loxodonta africana population of Mozambique has declined rapidly over the last 4 decades. Historical census data are incomplete but suggest that the impact of human activity on the elephant population increased after the onset of the colonial era. Demand for ivory explains the population decline from 1700 to 1940, and the killing of elephants as part of settlement policies and tsetse fly control programmes further reduced the populations between 1940 and 1960. Land transformation from 1900 onwards may also have contributed to the historical decline in elephant numbers. Our assessment suggests that landscape approaches should be explored in seeking to conserve elephants in modern Mozambique.

Modelling the effect of age-specific mortality on elephant Loxodonta africana populations: can natural mortality provide regulation?

The historical regulation of African elephant Loxodonta africana populations could provide guidelines for management efforts and decisions in areas where elephant numbers are now increasing. However, there are few detailed records of the natural mortality processes of the past. Therefore, we modelled elephant population growth to evaluate possible effects of age-specific mortality. Model projections indicated that an annual mortality of 17.1% of juveniles or 10.5% of adults would be sufficient to prevent population growth. For age classes below or just at sexual maturity (i.e. 0-3, 4-7, 8-11) 37.5% annual mortality of one of these classes was required to achieve 0% population growth. These mortality levels are much higher than those reported in southern Africa today. Simulations of episodic mortality events (e.g. droughts) indicated that such events would need to occur every 16 years at a severity that would cause the mortality of all infants and weaned calves (0-7 years old), as well as 10% of adults and subadults (8-60 years old) to prevent long-term population growth. An 8-year frequency required the mortality of 84.7% of infants and weaned calves. Historically, it is possible that high drought mortality and frequency, and high predation levels, may have reduced population growth significantly but current mortality rates and frequencies are insufficient to constrain long-term average population growth at 0%. The natural limitation of existent elephant populations through mortality is therefore unlikely, indicating a need for active management of the increasing elephant populations in southern Africa.

Detection of anthropogenic mortality in elephant Loxodonta africana populations: a long-term case study from the Sebungwe region of Zimbabwe

A survey of the Sebungwe elephant Loxodonta africana population in Zimbabwe in 2006 revealed a large rise in the number of dead elephants. The estimated number of carcasses increased >16-fold from 1989 to 2006 and the carcass ratio (number of all elephant carcasses as a percentage of the number of all elephants) rose from 1.25 to 15.4%. The ratio for fresh or recent carcasses, which reflected the mortality rate during the survey year, increased from 0.19 to 1.70% during 1995-2006. Records of elephants killed before 1995 were supplemented with estimates of the numbers killed after 1995, with these estimates increasing exponentially, as did the observed number of fresh or recent carcasses. A maximum likelihood analysis to compare population models revealed that the best fit to the survey estimates of this closed population was a model that started with 9,500 elephants in 1979 and that each year increased at 4.02% and decreased by the number killed, with the number killed annually increasing at 23.5% per year after 1995. A rise in anthropogenic mortality, mostly due to poaching, caused the increase in carcass numbers observed after 1999. Since 1997 the mortality rate of elephants in the National Parks and Safari Areas in the Sebungwe has been positively correlated with the observed number of poachers’ camps. Anthropogenic mortality is now great enough to keep the elephant population approximately constant at 14,000-16,000 animals. The population number was also constant (at a lower level) during the 1980s, when elephants were culled and the sale of meat, hides and ivory covered the costs of elephant management but there have been no recent culls, partly because the ivory trade ban prevents tusks from culled elephants being sold to offset the costs of management. This study illustrates the value of a long-term data set collected with consistent techniques, and including data on other species and the environment collected at no extra cost under the financial umbrella of a charismatic species.

Population management of zoo elephants

In Europe and North America the majority of Asian elephant Elephas maximus populations are not self‐sustaining nor is the African elephant Loxodonta africana population in North America. About 75% of Asian elephants in North America are wild‐caught or from semi‐wild logging camps and are presumed to be unrelated to the other Asian elephants in captivity. The genetic potential of these populations is healthy and will remain so if the demographic constraints impinging on them can be resolved. In order to become self‐sustaining the primary goal is to increase birth rates in the population, with a secondary goal of reducing infant‐mortality rates. As populations of elephants in zoos metamorphose from those maintained by importation to self‐sustaining groups maintained by captive breeding, there will be an increase in the number of bull elephants to be managed. This will require a significant change in elephant‐management practices.

Modelling and assessment of South African elephant Loxodonta africana population persistence

The use of a quantitative population growth model to investigate the persistence of South African elephant populations is explored. The model provides quantitative assessments of population persistence and confidence intervals for estimated parameters based purely on population size estimates. The analysis supports the view that most of the larger populations in the region are secure. This view is further supported by a lack of density dependent effects in most of the recovering populations and the high population rates of increase observed. This predominantly positive prognosis is in contrast with that emerging from most of the rest of the African continent where the populations are under greater threat because of habitat restriction and direct human conflict. This preliminary assessment of elephant population persistence suggests that “viable” populations may lie between 400 and 6000 individuals. Although not inconsistent with information-greedy genetic and demographic models, the relationship between population growth versus genetic and demographic models should be further investigated. The implementation of a metapopulation management strategy towards these smaller populations is advocated. In addition, as all of the populations included in this analysis have been afforded some degree of protection since the 1920s, continued protection would be a prerequisite for their continued survival.

The impact of the ivory trade on the African elephant Loxodonta africana population as assessed by data from the trade

Data on the total quantity and tusk sizes of African elephant Loxodonta africana ivory entering the international trade over the last decade are reviewed. This work investigated how different levels of hunting and different strengths of selectivity by hunters in favour of larger tusks would produce different ivory tonnages and tusk size distributions in the trade. It shows that the removal of about 12–13% of elephants with tusks each year, combined with hunters showing a preference for elephants with larger tusks, would be expected to produce quantities of ivory and tusk size distributions compatible with those reported in international trade.

Of Elephants and Men: A Discrete, Stochastic Model for Long-Lived Species with Complex Life Histories

Previous articleNext article No AccessOf Elephants and Men: A Discrete, Stochastic Model for Long-Lived Species with Complex Life HistoriesLilian Shiao-Yen Wu, and Daniel B. BotkinLilian Shiao-Yen Wu Search for more articles by this author , and Daniel B. Botkin Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 116, Number 6Dec., 1980 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/283672 Views: 8Total views on this site Citations: 12Citations are reported from Crossref Copyright 1980 The University of ChicagoPDF download Crossref reports the following articles citing this article:Timothy R. Kuiper, Dave J. Druce, Heleen C. Druce, Susan Cheyne Demography and social dynamics of an African elephant population 35 years after reintroduction as juveniles, Journal of Applied Ecology 55, no.66 (Jul 2018): 2898–2907.https://doi.org/10.1111/1365-2664.13199Blaire Van Valkenburgh, Matthew W. Hayward, William J. Ripple, Carlo Meloro, V. Louise Roth The impact of large terrestrial carnivores on Pleistocene ecosystems, Proceedings of the National Academy of Sciences 113, no.44 (Oct 2015): 862–867.https://doi.org/10.1073/pnas.1502554112Joel E. Cohen Stochastic Demography, (Nov 2014).https://doi.org/10.1002/9781118445112.stat00139Robin L. Mackey, Bruce R. Page, Douw Grobler, Rob Slotow Modelling the effectiveness of contraception for controlling introduced populations of elephant in South Africa, African Journal of Ecology 47, no.44 (Dec 2009): 747–755.https://doi.org/10.1111/j.1365-2028.2009.01075.xLeigh-Ann Woolley, Joshua J. Millspaugh, Rami J. Woods, Samantha Janse van Rensburg, Robin L. Mackey, Bruce Page, Rob Slotow, Robert Brooks Population and Individual Elephant Response to a Catastrophic Fire in Pilanesberg National Park, PLoS ONE 3, no.99 (Sep 2008): e3233.https://doi.org/10.1371/journal.pone.0003233Leigh-Ann Woolley, Robin L. Mackey, Bruce R. Page, Rob Slotow Modelling the effect of age-specific mortality on elephant Loxodonta africana populations: can natural mortality provide regulation?, Oryx 42, no.0101 (Feb 2008).https://doi.org/10.1017/S0030605308000495Joel E. Cohen Stochastic Demography, (Aug 2006).https://doi.org/10.1002/0471667196.ess2584.pub2I Hary Derivation of steady state herd productivity using stage-structured population models and mathematical programming, Agricultural Systems 81, no.22 (Aug 2004): 133–152.https://doi.org/10.1016/j.agsy.2003.10.007Milani Chaloupka Stochastic simulation modelling of southern Great Barrier Reef green turtle population dynamics, Ecological Modelling 148, no.11 (Feb 2002): 79–109.https://doi.org/10.1016/S0304-3800(01)00433-1 The exploitation of elephants for the ivory trade: an historical perspective, Proceedings of the Royal Society of London. Series B: Biological Sciences 252, no.13331333 (Jan 1997): 29–37.https://doi.org/10.1098/rspb.1993.0042E.J. Milner-Gulland, Ruth Mace The impact of the ivory trade on the African elephant Loxodonta africana population as assessed by data from the trade, Biological Conservation 55, no.22 (Jan 1991): 215–229.https://doi.org/10.1016/0006-3207(91)90057-G Katherine Wolf , and Steven Robert Schulman Male Response to "Stranger" Females as a Function of Female Reproductive Value Among Chimpanzees, The American Naturalist 123, no.22 (Oct 2015): 163–174.https://doi.org/10.1086/284195

The influence of the African Elephant on the vegetation of the Addo Elephant National Park

An increasing elephant Loxodonta africana population has been confined to a 2 770 ha enclosure since 1954. When compared to the vegetation adjacent to the enclosure, the plant biomass within has been reduced by more than one half. Changes in the botanical composition are described.