'Remote' behavioural ecology: do megaherbivores consume vegetation in proportion to its presence in the landscape?

Examination of the feeding habits of mammalian species such as the African elephant (Loxodonta africana) that range over large seasonally dynamic areas is exceptionally challenging using field-based methods alone. Although much is known of their feeding preferences from field studies, conclusions, especially in relation to differing habits in wet and dry seasons, are often contradictory. Here, two remote approaches, stable carbon isotope analysis and remote sensing, were combined to investigate dietary changes in relation to tree and grass abundances to better understand elephant dietary choice in the Kruger National Park, South Africa. A composited pair of Landsat Enhanced Thematic Mapper satellite images characterising flushed and senescent vegetation states, typical of wet and dry seasons respectively, were used to generate land-cover maps focusing on the forest to grassland gradient. Stable carbon isotope analysis of elephant faecal samples identified the proportion of C3 (typically browse)/C4 (typically grass) in elephant diets in the 1-2 days prior to faecal deposition. The proportion of surrounding C4 land-cover was extracted using concentric buffers centred on faecal sample locations, and related to the faecal %C4 content. Results indicate that elephants consume C4 vegetation in proportion to its availability in the surrounding area during the dry season, but during the rainy season there was less of a relationship between C4 intake and availability, as elephants targeted grasses in these periods. This study illustrates the utility of coupling isotope and cost-free remote sensing data to conduct complementary landscape analysis at highly-detailed, biologically meaningful resolutions, offering an improved ability to monitor animal behavioural patterns at broad geographical scales. This is increasingly important due to potential impacts of climate change and woody encroachment on broad-scale landscape habitat composition, allowing the tracking of shifts in species utilisation of these changing landscapes in a way impractical using field based methods alone.

Multi-tissue analysis of oxygen isotopes in wild rhesus macaques (Macaca mulatta).

Oxygen isotopes in animal tissues are directly related to body water composition and thus the environment. Accurate measurement of animal tissue δ(18)O provides information about local climate, an animal's geographical origin and subsequent movements, with wide applications in palaeobiology and forensic science. The genesis and evolution of tissue-based oxygen isotopes within species and within individuals are complex. We present the first data, for non-human primates, rhesus macaques (Macaca mulatta), on the relationship between oxygen isotope sources in bio-apatite (PO(4) and PCO(3)) and hair taken from six sample sites in Asia, ranging from western India to northern Vietnam. The range of values is similar within each tissue type, with good correlation between tissues (r = 0.791 to 0.908), allowing cross-tissue extrapolations. This is important when the availability of suitable tissues is limited. Biological interpretation of the small data set is difficult: macaque diets are eclectic, and the samples are from various locations. However, factors such as overall climate, precipitation quantity and source, and altitude are clearly influencing the results for each discrete geographical grouping. Future work could be aimed at assessing δ(18)O tissue associations for other species as the relationships appear to be species-specific.

Modern macaque dietary heterogeneity assessed using stable isotope analysis of hair and bone.

Dietary variability might have been a major factor in the dispersal and subsequent persistence of the genus Macaca in both tropical and temperate areas. Macaques are found from northern Africa to Japan, yet there have been few systematic attempts to compare diets between different modern populations. Here we have taken a direct approach and sampled museum-curated tissues (hair and bone) of Macaca mulatta (rhesus macaques) for carbon and nitrogen stable isotope dietary analyses. Samples from India, Vietnam, and Burma (Myanmar) were taken, representing both tropical and temperate populations. The delta(13)C values obtained from hair show that the temperate macaques, particularly those from Uttar Pradesh, have a delta(13)C signature that indicates at least some use of C(4) resources, while the tropical individuals have a C(3)-based diet. However, delta(13)C values from bone bioapatite indicate a C(3)-based diet for all specimens and they do not show the C(4) usage seen in the hair of some animals, possibly because bone represents a much longer turnover period than that of hair. The results of delta(15)N analyses grouped animals by geographic region of origin, which may be related to local soil nitrogen values. The greatest variation in delta(15)N values was seen in the specimens from Burma, which may be partly due to seasonality, as specimens were collected at different times of year. We also investigated the relationship between the hair, bone collagen, and bone bioapatite delta(13)C results, and found that they are highly correlated, and that one tissue can be used to extrapolate results for another. However, our results also suggest that hair may pick up discrete feeding traces (such as seasonal usage), which are lost when only bone collagen and bioapatite are examined. This has important implications for dietary reconstructions of archaeological and paleontological populations.

Theropithecus and 'Out of Africa' dispersal in the Plio-Pleistocene.

Theropithecus oswaldi was one of the most widely distributed Plio-Pleistocene primates, found in southern, East, and North Africa, as well as in Spain, India, and possibly Italy. Such a large geographic range for a single primate species is highly unusual. Here, the nature and timing of its dispersal is examined using the Stepping Out cellular automata model. A hypothetical dispersal of T. darti is also modelled to assess whether the late Pliocene might have been a more favorable period for Afro-Eurasian dispersal than the early Pleistocene. Stepping Out draws on climatic and biome reconstruction to provide the paleovegetative and climatic background necessary for the simulations, and model parameters for T. oswaldi and T. darti were set a priori on the basis of their fossil records and paleobiologies. The simulations indicate that T. darti could have readily left Africa in the Pliocene, and that it swiftly reaches Asia. A European T. darti colonization was less certain and less rapid. The simulated T. oswaldi dispersal out of Africa was slower, but nonetheless T. oswaldi arrived at Mirzapur within the time period indicated by the fossil record. Using the a priori parameters, T. oswaldi did not arrive at the European sites of Cueva Victoria and Pirro Nord. It cannot be discounted, therefore, that some of the European fossils are a result of an earlier T. darti dispersal. The simulations also showed that in order for Theropithecus to reach Europe, it needed to be tolerant of a relatively wide range of habitats. In addition, our finding that Asian colonization was more rapid and more probable parallels the information from the hominin fossil record, in which the fossils from Asia predate those from Europe by several hundred thousand years.