Severe drought and calf survival in elephants

Foley, Charles; Pettorelli, Nathalie; Foley, Lara

doi:10.1098/rsbl.2008.0370

Cited by 183 publications

(172 citation statements)

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“…This is very far from our sustainable harvest estimates (Figure 4). These estimates do not account for population variance in tusk size and tusklessness [16], indirect social effects of the harvest [17] and abiotic effects on demography [11]. Climate predictions show that droughts will intensify and become more frequent [18] hence the population trajectory we simulated is liberal (note how we are not capturing extreme changes, Figure 1C).…”

Section: Harvest Sustainabilitymentioning

confidence: 94%

“…In this instance, the population model was parameterised using information from the longest running research programme on African elephants. It is important to note that in this model we accounted for neither stochastic environmental impacts on demographic rates (droughts [11]), nor indirect social demographic effects (e.g., the impact of matriarchs on survival probability in their matrilines [12]). Therefore, the population trajectory we simulate is the best this population can achieve.…”

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confidence: 99%

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Can We Sustainably Harvest Ivory?

Lusseau

Lee

2016

Current Biology

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SUMMARYDespite the 1989 ivory trade ban, elephants continue to be killed to harvest their tusks for ivory. Since 2008, this poaching has increased to unprecedented levels driven by consumer demand for ivory products. CITES is now considering to develop a legal ivory trade [1,2]. The proposal relies on three assumptions: i) harvest regulation will cease all illegal activities; ii) defined sustainable quotas can be enforced; iii) we can define meaningful sustainable quotas that come close to the current demand. We know that regulating harvest does not stop illegal takes. Despite whaling regulation after WWII, illegal whaling continued for decades [3]. The introduction of wolf culls in the USA actually increased poaching activities [4] while one-off ivory sales in 1999 and 2008 did nothing to halt elephant poaching. Governance issues over the ivory supply chains, including stockpiling, make enforcing quotas challenging if not impossible [5,6]. We have not yet adequately assessed what could be a sustainable ivory yield. To do so, we develop a compartmental model composed of a two-sex agestructured demographic model and an ivory production and harvest model. We applied several offtake and quota strategies to define how much ivory could be sustainably harvested. We found that the sustainability space is very small. Only 100 to 150kg of ivory could be removed from a reference population of 1360 elephants, levels well below the current demand. Our study shows that lifting the ivory ban will not address the current poaching challenge. We should instead focus on reducing consumer demand. RESULTS AND DISCUSSIONHarvest model development In order to develop a harvest model, we must first understand the process by which ivory is obtained. We can apply one of the many approaches used in wildlife management to define these sustainable quotas. However, much of the debate surrounding the sustainability of ivory harvest overlooks one key point: hunters do not want to kill elephants; they want to harvest ivory. Yet, we attempt to inform this harvest using one of two approaches, neither suited to the challenge. It is misguided to use classical population models to try and predict what level of elephant removal population(s) can sustain so as to provide the ivory needed for the market because ivory requires selective harvesting from a sexually dimorphic trait [7]. It is also misguided to use classical resource extraction models, which the current CITES "Decision-Making Mechanism for a Process of Trade in Ivory" is considering, because ivory is a renewable resource made by elephants which increases in mass as elephants age [2]. If the take does not match the demographic pace of elephant populations, a given amount of ivory harvested by removing a few large elephants from the population will require killing more, smaller, elephants the next year. We faced a similar hurdle in the early 20 th century when trying to manage whaling by reducing the harvest to the amount of whale oil produced when that oil was extracted from different age-se...

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Section: Harvest Sustainabilitymentioning

confidence: 94%

mentioning

confidence: 99%

Can We Sustainably Harvest Ivory?

Lusseau

Lee

2016

Current Biology

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“…These remarkable feats suggest exceptional cognitive mapping skills, reliant on the long-term memories of older individuals who travelled that path sometimes decades earlier. Indeed, a recent study has confirmed that family groups with older matriarchs are better able to survive periods of drought (Foley, Pettorelli, & Foley, 2008). Families with older matriarchs range over larger areas during droughts, apparently drawing on the knowledge of the older females about the locations of permanent, drought-resistant sources of food and water.…”

Section: Space and Objectsmentioning

confidence: 99%

Elephant cognition in primate perspective

Byrne¹,

Bates²,

Moss

2009

CCBR

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On many of the staple measures of comparative psychology, elephants show no obvious differences from other mammals, such as primates: discrimination learning, memory, spontaneous tool use, etc. However, a range of more naturalistic measures have recently suggested that elephant cognition may be rather different. Wild elephants sub-categorize humans into groups, independently making this classification on the basis of scent or colour. In number discrimination, elephants show no effects of absolute magnitude or relative size disparity in making number judgements. In the social realm, elephants show empathy into the problems faced by others, and give hints of special abilities in cooperation, vocal imitation and perhaps teaching. Field data suggest that the elephant's vaunted reputation for memory may have a factual basis, in two ways. Elephants' ability to remember large-scale space over long periods suggests good cognitive mapping skills. Elephants' skill in keeping track of the current locations of many family members implies that working memory may be unusually developed, consistent with the laboratory finding that their quantity judgements do not show the usual magnitude effects.

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“…Many animals are postulated to use cues from more knowledgeable conspecifics (e.g. elephants (Blake et al 2009;Polansky et al 2015;Foley et al 2008) or from heterospecifics (Saracco et al 2004) to help them identify and navigate to resources or may follow trails left by conspecifics (e.g. Blake and Inkamba-Nkulu 2004).…”

Section: Introductionmentioning

confidence: 99%

Plant ecology meets animal cognition: impacts of animal memory on seed dispersal

et al. 2016

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We propose that an understanding of animal learning and memory is critical to predicting the impacts of animals on plant populations through processes such as seed dispersal, pollination and herbivory. Focussing on endozoochory, we review the evidence that animal memory plays a role in seed dispersal, and present a model which allows us to explore the fundamental consequences of memory for this process. We demonstrate that decision-making by animals based on their previous experiences has the potential to determine which plants are visited, which fruits are selected to be eaten from the plant and where seeds are subsequently deposited, as well as being an important determinant of animal survival. Collectively, these results suggest that the impact of animal learning and memory on seed dispersal is likely to be extremely important, although to date our understanding of these processes suffers from a conspicuous lack of empirical support. This is partly because of the difficulty of conducting appropriate experiments but is also the result of limited interaction between plant ecologists and those who work on animal cognition.We believe that an improved understanding of the effects of animal memory in endozoochorous interactions will allow better prediction of the impacts of ecosystem changes such as habitat fragmentation, introductions of novel species of plants and animals and reintroductions of animal populations to areas from which they have been extirpated, and hope that the ideas we put forward here provide an impetus for further work in this area.

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Severe drought and calf survival in elephants

Cited by 183 publications

References 10 publications

Can We Sustainably Harvest Ivory?

Can We Sustainably Harvest Ivory?

Elephant cognition in primate perspective

Plant ecology meets animal cognition: impacts of animal memory on seed dispersal

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