Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 81.82K | Year: 2011
The race for survival is common to all living organisms: when it comes to predator-prey interactions, this involves predators developing more effective means to catch prey whilst their prey counteracts with new evasion tactics. Energy is a primary limiting resource in most natural systems. To understand how energy budgets compel certain species to inhabit specific environments, it is necessary to identify a species that displays extreme energy requirements. Within mammals, large predators often experience high energy costs while hunting and it is suggested that this may restrict their ecological niches, obliging them to inhabit only areas with abundant food sources and minimal competition. However, no study has yet attempted to measure energy expenditure in a large carnivore while simultaneously monitoring interactions between competitors and prey. With the greatest power output for their size of any mammal and the greatest speed reached on land, cheetahs (Acinonyx jubatus) are positioned at an apex in the topography of evolutionary adaptation. Does such an evolutionary peak come with a cost? Research suggests cheetahs are severely restricted in their abilities to acquire and utilise energy. In the current study, we will measure energy expenditure in free-ranging cheetahs to determine which behaviours or circumstances cause particular energetic constraints. Cheetahs are built for speed, accelerating from 0 to 30 kph in three strides and reaching a maximum speed of about 110 kph in 4 seconds. At full speed, the cheetah is running at about three strides per second and the respiratory rate climbs from 60 to 150 breaths per minute. Cheetahs can only maintain this for a few hundred metres before exhaustion. Such a high-speed foraging strategy imposes severe limits on all other aspects of their lives, leaving them vulnerable to starvation, or to reproductive failure due to lack of energy. This is because their predation tactics are energetically costly, and, being built for speed rather than strength, they are easily driven off their prey by more robust rival species. Consequently, cheetahs are suggested to be at an energetic edge, with the viability both of individual animals and populations depending on how close individuals approach the evolutionary limits of energy supply and demand. An understanding of their energetic tactics will therefore help provide insights as to how energetic constraints can shape the evolution of these super-predators. Energy use will be measured using the doubly labelled water technique  whilst field observations will be made of activities and of incidents where rival species steal prey or interact with cheetahs in other ways that may affect their energy balances. In addition, multi-channel data loggers -daily diaries - will be attached to the cheetahs using collars for up to 80 days at a time. These devices provide data on detailed movement in three dimensions  at a very fine resolution (32 Hz). Interpretation of the resulting electronic traces recorded will reveal the time spent on various activities such as resting, feeding, walking and running. The data will also be used to calculate a proxy of energy expenditure, known as overall dynamic body acceleration. This will complement the energetics data and provide a fine-scale record of continuous activity. Thus, individual activities and their associated energy costs will be elucidated to paint a complete picture of the animals energy budgets. The study will provide valuable information as to how carnivores in general manage their energy budgets. It will also demonstrate how the measurement of physiological characteristics can help determine the long-term viability of rare and threatened species. Thus we shall be providing insights into how energetic constraints can shape species viability.  Speakman, J.R. Doubly Labelled Water. 1997. Chapman and Hall.  Wilson, R.P. et al. 2008 Endang. Species. Res. 3:1-15
Gomes I.,Global Vision International GVI |
Erzini K.,University of Algarve |
Mcclanahan T.R.,Wildlife Conservation Society
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2014
Innovative strategies are needed to escape the social-ecological poverty that so frequently emerges from persistent overfishing of coral reef resources.This study focuses on fishing gear selectivity and its potential to increase ecosystem health and fisheries productivity without compromising the catch of profitable species.An investigation into the effects of an escape gap (3cm × 30cm) modification to the traditional African basket trap on total catch biomass, catch composition and monetary value in two locations with different historical levels of fishing was undertaken.Gated traps caught less low-value fish (juveniles and narrow-bodied coral reef species) while increasing the catch of high- and medium-value fish (wider-bodied commercially valuable species). The total monetary value of the gated trap catches was maintained in a heavily fished environment, while it increased in the less fisheries-depleted area.For the most important local commercial species, the African white-spotted rabbitfish (Siganus sutor), the gated traps significantly increased the mean length (by 12%) and weight (by 32%) of capture and decreased the proportion of catch under length at first maturity (Lmat) from 56% (traditional traps) to 25% (gated traps).Escape gaps have shown the potential to affect the structure of the fishery and ecosystem by enhancing the number of mature individuals, increasing reef biodiversity and promoting functionally diverse reef fish communities without compromising fisher's revenues. © 2013 John Wiley & Sons, Ltd.