Movement and dietary preferences of migratory ungulates as estimated from stable isotope ratios in tail hair

Globally, ungulate populations face considerable threats from human activities, which have resulted in the global decline (and local extinction) of major ungulate species including the African elephant (Loxodonta Africana), the black rhinoceros (Diceros bicornis) and most recently, the African giraffe (Giraffa camelopardalis) . However, the most common animal response is movement, and the most common human mitigation strategy has been expanding coverage of protected areas. Yet, a significant loss of ungulates’ species and biodiversity has been reported across different protected areas, suggesting that expanding protected areas alone might not be the most effective solution. Restoring historical connectivity and migratory corridors might offer a more sustainable and manageable solution. However, to effectively apply conservation and restoration methods, historical information on the extent of animal movement patterns as well as their dietary preferences is of utmost importance. Yet, answering the question of where, how and why animals move has always been methodologically challenging, limiting our understanding of the extent of their movements as well their associated dietary preferences. The use of tracking devices and other traditional methods for studying animal movement has proven expensive and can pose serious concerns for animal welfare. Furthermore, studying movement retrospectively is impossible using the aforementioned techniques. Stable isotope ratio analysis techniques offer an alternative solution for exploring animal movement that is relatively cheap, easy to interpret and more importantly non-invasive to individual animals. Furthermore, the technique offers a possibility of understanding the historical range of animal movements retrospectively using archived materials such as specimens from museums. The primary contribution of this thesis is to demonstrate the applicability of isotopic analysis of tail hair to studies of movement and dietary interactions of migratory ungulates using the Serengeti ecosystem in East Africa as a case study. The use of tail hair is promising because it represents a less-invasive way of recreating time series information of animal’s movement and feeding history. The Serengeti ecosystem presents a powerful model system to explore the use of isotopic methods applied to the tail hair of migratory ungulates because it harbors more than 27 species of ungulates including the migratory blue wildebeest (Connochaetes taurinus) and plain zebra (Equus quagga). Furthermore, the ecosystem has a diversity of soil types as influenced by the underlying geological parent material, which gives the ecosystem a strong spatial variability in the isotope values. The study presented here seeks to: demonstrate the potential of utilizing a less-invasive technique of stable isotope ratios in tail hairs to investigate animal movement. Then, to examine the feasibility of using isotopic ratios in tail hair for geolocating migratory animals. Furthermore, the study aims to demonstrate how isotopic ratios in tail hair can help to distinguish between resident and migrant life history strategies in a mixed population. And lastly, to employ isotopic ratios in tail hair to gain insight into the periods of dietary convergence and partitioning during the annual cycle of co-migrating species. Using spatial generalized additive model (GAM), this study establishes an interpolated map for the variation of sulfur stable isotope ratios (δ 34S) in the grass across the Serengeti ecosystem (hereby referred to as the δ 34S isoscape). The isoscape was underpinned by a positive relationship between δ 34S and the local lithology. Using tail hairs sampled from cattle (Bos taurus), the created isoscape is used to test the hypothesis that δ 34S in tail hair reflects the δ 34S values of the diet (in this case, grass), and they can therefore be used for animal geolocation. Through a series of mathematical models and tail hair samples from GPS collared wildebeest, the δ 34S isoscape is used to identify the scenarios in which δ 34S in the tail hair are useful in the analysis of movement of migratory animals. Furthermore, I show using a series of state-space models of animal movement, how the δ 34S isoscape can be used in combination with variation of δ 34S in tail hair to differentiate resident versus migrant life-history forms of wildebeest. Using Stable Isotope Mixing Models (SIMMs), stable isotope ratios of carbon (δ 13C) and nitrogen (δ 15N) in the tail hair of wildebeest and zebra are used to understand seasonal periods of diet convergence and partitioning for the co-migrating animal species. The results of this study suggest that the Serengeti ecosystem has strong spatial variability in δ 34S across its geological ranges. Furthermore, the results suggest that the δ 34S values in the tail hair strongly reflect the δ 34S values in the grass, suggesting that the variation of δ 34S in the tail hair can be used as a natural bio-logger for differentiating local versus non local movement of animals. The output from the mathematical models suggests that the values of δ 34S take an average of 78 days from when the forage is ingested to isotope reflection in the tail hair of migratory wildebeest, suggesting that δ 34S might not be as effective for geolocating large mobile animals. On the other hand, the results from state-space models of animal movement suggest that the variation of δ 34S in the tail hair is effective in differentiating resident from migrant life history strategies. This finding led to the creation of a classification key for identifying resident versus migrant life-histories. Results from SIMMs have demonstrated that, using time-series information generated from tail hair samples, we can detect the periods of diet convergence versus diet partitioning between co-migrating animals. For example, the highest dietary niche overlap between wildebeest and zebra has been observed in August and the lowest in May. This finding suggests that we can identify periods of strong competition for pasture and possible mitigations that species take to maintain their co-existence using stable isotope ratios technique. The results from this thesis highlight the importance and application of isotopic methods to understand movement and dietary preferences of migratory ungulates. The created δ 34S isoscape for the Serengeti acts as a baseline from which other isotopic studies can be conducted. Furthermore, the study has developed a classification key which can be adopted, modified and applied to a diversity of taxa for identifying resident and migrant life-histories. The study has further helped an understanding of niche partitioning and coexistence of species especially in biodiverse regions where multiple species all focus on the same general resource

Increasing importance of nitrate-nitrogen and organic nitrogen concentrations in bulk and throughfall precipitation across urban forests in southern China

Atmospheric nitrogen (N) deposition is an increasingly serious threat to forest ecosystems requiring urgent global actions. While it is well-known that developing countries are experiencing rapid urbanization, an understanding of its effects on N composition and sources in atmospheric deposition is only beginning to emerge. We measured dissolved inorganic N (DIN), dissolved organic N (DON) and total dissolved N (TDN) concentrations in bulk precipitation (BP) and throughfall precipitation (TP) across four seasons in forest ecosystems along the more urbanized river (Bailongjiang; BJR) and the less urbanized river (Wulongjiang; WJR) in Fuzhou coastal city. Concentrations of all N forms were greatly enhanced in BJR forests than in WJR forests, suggesting increased anthropogenic N pollution in forests along the BJR that, in turn, can cause serious N cycle perturbations. While precipitation N concentrations over the BJR forests were primarily influenced by pollutants from fossil fuel combustion activities (ammonium-nitrogen; NH4 +-N/nitrate-nitrogen; NO3 −-N = 0.77), those over the WJR forests were collectively influenced by pollutants from fossil fuel combustion and agricultural activities (NH4 +-N/NO3 −-N = 1.14). The DON contributed 22–38% of N to the TDN across seasons and rivers and was positively related to other N forms, indicating that DON is steadily becoming a vital component in atmospheric N deposition especially in anthropogenically N-polluted atmospheres. Summer was characterized by precipitation with lower N concentrations, highlighting increased dilution effect and decreased anthropogenic N emissions. Nitrogen concentrations were more elevated in TP than in BP, suggesting that tree canopies augment atmospheric N deposition to forest soils. Generally, soil and foliar TN and δ15N were positively related to precipitation TDN, indicating that increased atmospheric N deposition enhances forest ecosystem N availability. Our results demonstrate that urban areas particularly in developing countries are not only NHx but also NOx emission and deposition hotspots and emphasize the necessity of including them in future global N budgets and N pollution abatement initiatives

Using sulfur stable isotope ratios (δ34S) for animal geolocation: estimating the delay mechanisms between diet ingestion and isotope incorporation in tail hair.

Rationale: Metabolism and diet quality play an important role in determining delay mechanisms between an animal ingesting an element and depositing the associated isotope signal in tissue. While many isotope mixing models assume instantaneous reflection of diet in an animal– tissue, this is rarely the case. Here we use data from wildebeest to measure the lag time between ingestion of 34S and its detection in tail hair. Methods: We use time-lagged regression analysis of δ34S data from GPS-collared blue wildebeest from the Serengeti ecosystem in combination with δ34S isoscape data to estimate the lag time between an animal ingesting and depositing 34S in tail hair. Results: The best fitting regression model of δ34S in tail hair and an individual– position on the δ34S isoscape is generated assuming an average time delay of 78 days between ingestion and detection in tail hair. This suggests that sulfur may undergo multiple metabolic transitions before being deposited in tissue. Conclusion: Our findings help to unravel the underlying complexities associated with sulfur metabolism and are broadly consistent with results from other species. These findings will help to inform research aiming to apply the variation of δ34S in inert biological material for geolocation or understanding dietary changes, especially for fast moving migratory ungulates such as wildebeest

Tracking animal movements using biomarkers in tail hairs: a novel approach for animal geolocating from sulfur isoscapes.

This research article published by Movement Ecology, 2020Background Current animal tracking studies are most often based on the application of external geolocators such as GPS and radio transmitters. While these technologies provide detailed movement data, they are costly to acquire and maintain, which often restricts sample sizes. Furthermore, deploying external geolocators requires physically capturing and recapturing of animals, which poses an additional welfare concern. Natural biomarkers provide an alternative, non-invasive approach for addressing a range of geolocation questions and can, because of relatively low cost, be collected from many individuals thereby broadening the scope for population-wide inference. Methods We developed a low-cost, minimally invasive method for distinguishing between local versus non-local movements of cattle using sulfur isotope ratios (δ34S) in cattle tail hair collected in the Greater Serengeti Ecosystem, Tanzania. Results We used a Generalized Additive Model to generate a predicted δ34S isoscape across the study area. This isoscape was constructed using spatial smoothers and underpinned by the positive relationship between δ34S values and lithology. We then established a strong relationship between δ34S from recent sections of cattle tail hair and the δ34S from grasses sampled in the immediate vicinity of an individual’s location, suggesting δ34S in the hair reflects the δ34S in the environment. By combining uncertainty in estimation of the isoscape, with predictions of tail hair δ34S given an animal’s position in the isoscape we estimated the anisotropic distribution of travel distances across the Serengeti ecosystem sufficient to detect movement using sulfur stable isotopes. Conclusions While the focus of our study was on cattle, this approach can be modified to understand movements in other mobile organisms where the sulfur isoscape is sufficiently heterogeneous relative to the spatial scale of animal movements and where tracking with traditional methods is difficult

Habitat utilisation and nesting behaviour of two sympatric weavers in Mbalmayo District, Cameroon

Avian ecology and behaviour data provides crucial information for bird conservation and management, but are still missing for many species, particularly in developing countries. This study examines habitat utilisation, nesting behaviour, anthropogenic disturbances and impacts on agricultural crops of Village Weaver Ploceus cucullatus and Vieillot’s Black Weaver Ploceus nigerrimus in Mbalmayo District, Cameroon. Abundance was estimated by nest counts and point counts of birds at 40 previously located colonies, where also tree metrics and anthropogenic disturbances were measured. In total, more than 1 700 birds of the two species were estimated within a 9 km2 study area, divided into two blocks and five different habitat types. Village Weavers were generally more abundant, especially in the urban habitat, whereas Vieillot’s Black Weavers were most numerous in the rural habitat. Among the tree species used for nesting, mango Mangifera indica and African border tree Newbouldia laevis had the highest nest counts, which also was positively related to canopy cover diameter. Traffic noise disturbance was associated with lower bird and nest counts, whereas the opposite was observed on farming disturbance. The relative impacts on agricultural crops were estimated for African oil palm Elaeis guineensis (38%), maize Zea mays (36%), Musa spp. (18%) and Mangifera indica (8%). The implications for long-term coexistence between farmland birds and humans are discussed, and the challenge is to minimise both kinds of bird–human interactions, i.e. anthropogenic disturbances and agricultural crop damage