People: Alan Wilson, Oliver Dewhirst, Tatjana Hubel, Simon Wilshin, Kyle Roskilly, Nancy Curtin, Timothy West, Maria Lorenc, Steve Amos, Chris Buse, John Lowe, Anna Wilson, Hattie Bartlam-Brooks

The LOCATE project studies the locomotion and hunting behaviours of large African carnivores, animals with no domestic counterparts and which live at the extremes of performance in speed, agility and strength. 

Leopard snarling in a tree

South African carnivores are among the most threatened species in the world but remain poorly understood in many aspects. There is still much to learn about how they achieve the speed and dexterous manoeuvring required in hunting, or how their prey has learned to compete with that. We also do not know the details of the interplay between animal and habitat during hunts, and what habitat features can make the crucial difference between a catch or escape. Another area of unknown is the daily migration of the animals, and how far they travel in a day or night.

The LOCATE project, led by Professor Alan Wilson, is a collaborative effort of interdisciplinary researchers and engineers to address these questions in a single, cohesive study. As these are issues that have direct ramifications on the delicate balance between survival success and failure, this research has the potential to contribute to the preservation of these endangered species.

Predators and Prey

The LOCATE project studies two symbiotic groups of animals in their natural habitat of the African savannah.

A collared cheetah on an antelope kill
Cheetah with its kill

The first group are cursorial predators: lions, leopards, cheetahs, African wild dogs and hyenas, which all catch prey after a period of pursuit where acceleration, speed, endurance and agility are critical to the outcome of the hunt. It is essential for the predator's hunting tactics to be successful frequently enough for the food gained to replenish energy in excess of the metabolic cost expended hunting. This is already an unstable balance, and when the predator is rearing and providing for young this margin between energy requirements and expenditure grows even larger. These hunting tactics are attributed to the predator's body size, group size, ability to hunt as a group, endurance, speed and agility, and so vary with each species individual traits. The species LOCATE studies are locomotor extremists; cheetahs are the fastest animals on land, and wild dogs are almost unparalleled in their endurance. Locomotion is an important feature of their lifestyle and success and they occupy well-understood ecological niches.

The second study group are representative species of the predators’ main herbivore prey in the study area: impala, zebra, steenbok, kudu and wildebeest which run and manoeuvre to evade capture; some also travel significant distances to feed and get water.

Our goal is to understand the locomotion of both daily living - such as in foraging, mating or migrating -  and during hunting/being hunted. We will also investigate the role of habitat morphology in hunting and evasion strategy and tactics.

Objectives of the LOCATE project

  1. Determine the dynamics, mechanics and extent of economical and extreme locomotion in predator and prey using innovative technology.
  2. Determine the muscle physiology including power and economy of muscle tissue from some of the same species using field measurements to characterise muscle environment (contraction speed, duty cycle at preferred speeds) and dissections to determine musculoskeletal arrangement.
  3. Study locomotor behaviour and ecology from an energetic and ecological perspective: ranging cost, group hunting strategies, habitat use in relation to predation and hunting, locomotor strategies in response to limited resources (water, food).

How will the animals be studied?

Lion with RVC tracking collar
Lion with RVC tracking collar

Collars

Being at the forefront of research necessitated us engineering our own innovative collars (containing high accuracy GPS, accelerometers, gyroscopes and compasses) to record all aspects of the locomotion activity of the carnivores and their prey. The collars function for at least a year without human contact. Data is collected from the collars periodically by a remote upload facility, either from the ground from a distance of up to 80m or from the air.

Aerial data collection

Two different aerial platforms give us the opportunity to collect data from the study animals with minimal disturbance, and to gather terrain and vegetation data from the study area.

The first platform is our own research aeroplane, equipped with high-speed high-resolution video to automatically track and film hunting in action by ‘locking on’ to the GPS co-ordinates of the collar. Cameras and LiDAR from the plane produce detailed scans of the ground profile and vegetation.

Read more about the research aircraft here.

The second aerial platform is an unmanned air vehicle (UAV) which tracks and films during the day and also continues data collection when the manned plane cannot fly at night by using infra-red cameras.

By using our long-life collars and a remote aerial platform for data collection and upload we minimise impact on the animals. The additional habitat description and utilisation data from LiDAR and aerial photography will further enhance this lifestyle data. This non-invasive method of data collection allows the findings to be reflective of normal behaviour as the subject animals are not distressed or perturbed by the research.  

Muscle studies

The primacy of highly adapted locomotor muscle performance for survival among these species makes them a fascinating subject of study. Certain predators in this study, such as leopards and lions, rely on stealth and extremely high muscle strength for prey capture. Cheetahs employ unequalled high speed and manoeuvrability to run down prey, requiring high muscle power/weight ratio. Spotted hyena and wild dogs rely on long endurance and economical moderate speed locomotion to capture prey.

Prey, particularly those that migrate, need to be economical for day-to-day locomotor activity but also have anatomy and strategy to evade the full spectrum of predator athleticism.

We want to find out how the arrangement and properties of the locomotor muscles in both predators and prey species reflect this specialisation/generalisation spectrum.

To relate what is happening at the muscle level to what is happening at the whole animal level, we need to compare muscle properties with locomotor performance. We will measure the characteristics of the muscles using in vitro experiments with small muscle samples from all our study species to determine muscle power, velocity and efficiency of generating force and work. We will also assess the endurance of the muscle samples and the way their properties are altered by fatigue. We hope these studies will inform us about how muscles are specialised for the different roles they have in different animals.

The study location

Most of the field research will be undertaken in Botswana. The study area is a 2,600km2 section in the wildlife management area of Northern Botswana adjacent to the Moremi Game Reserve. The area is characterised by mixed vegetation and habitat types including dry floodplains, large woodland areas and mopane shrubland. A full complement of indigenous wildlife species is present including 11 species of ungulates and 13 carnivores. All five of the large carnivores we wish to study are present here.

Study area with GPS base station in foreground
Study area with GPS base station in foreground


How will the results be used?

The study findings will be the first detailed data on the hunting and evasion capabilities of these species within a large predator-prey guild and will enable us to address important questions about differences in strategies and physical capabilities. The same data can be used to understand how the different species fit into their shared ecological niche. The non-invasive nature of the research means the findings accurately emulate normal behaviour, allowing ecologists to apply the results to a spectrum of study areas such as habitat management planning, migration, hunting and evasion strategies, and habitat use in predation and hunting. Muscle physiology study will characterise muscle properties such as contraction speed, muscle power and muscle efficiency. This will enable us to relate muscle level events to whole animal energetics and efficiency. 

The findings of LOCATE research have been published in several papers. In addition, the team have presented at various UK and international meetings. 

Our most recent study investigating the relative athleticism of predators and their main prey has been published in Nature. A summary of the paper is available here, and the study has been picked up by media sources including the New York Times, BBC News, Seeker, Science News, Forbes, Gizmodo, MailOnline, Africa Times, and Phys.Org.

New findings reporting that human modification of landscapes reduces the ranging distance of wild mammals was recently published in Science. RVC researcher Hattie Bartlam-Brooks contributed data on zebra movement to complete the dataset of over 800 individual mammals across 57 species. This study highlights the importance of human impact on the ecosystem.    

Our work has also been featured in the third episode of BBC One's Big Cats programme. 

Acknowledgement

We thank the European Research Council for funding this research (Advanced Grant 323041).

Project beginnings

The LOCATE project began in November 2013. In the preliminary stages of the project, work centered around darting and collaring animals. The study animals were sedated by a veterinary surgeon to allow researchers to fit them with collars. While the animal was sedated, this time was also used to take physiological and anatomical measurements, complete a health check on the animal, and for fine needle biopsies to be taken and sent to the UK laboratory for muscle physiology studies. All animals were monitored after sedation to ensure they re-joined their groups and fully recovered from the darting. All of the collared animals behaved normally and remained within the range of their usual territory, with none displaying any disturbance or distress from the collars.

Cheetah being collared and being given a health check

Data is routinely downloaded from the collars by remote electronic methods, in alignment with the goal of the study causing as little hindrance and disturbance to the animals as possible. The downloaded data are then transferred back to the UK lab for archiving and analysis, as well as shared with collaborators in Botswana for their research programmes. In Ghanzi we successfully piloted the use of automated download stations fixed in trees, a pioneering method of data collection. Clever use of ecology was paramount in the selection of trees to use in this way, as we established which trees were used with predictive regularity as marking trees and therefore which trees would be frequented by the study animals. Again, this minimised the impact of our work on the animals.

Tracking a Migration

In the summer of 2016, 33 GPS collars were deployed onto a migratory group of zebra and wildebeest to investigate movements and physiological adaptations of this unique population. This effort yielded several interesting, and some unexpected, findings.

Data from these collars demonstrated the effect unusual weather patterns can have on the movements of herbivore populations. The rains of this wet season were very late, posing a problem to these migratory zebras, who are known to initiate their migratory movements in response to rainfall events. Heavy storms trigger the zebra to embark on their migration but this movement is only completed if rainfall is sustained. The lack of early, continuous rainfall meant this trigger was absent, and may explain why only one of the seven collared zebra successfully migrated. Others attempted to migrate before turning back early, while some made no migratory efforts at all. This demonstrates the significant impact unusual climatic scenarios can have on animal behaviour, but also illustrates the resilience of zebra; despite the migratory failure, all the collared zebra survived the wet season, with the majority even going on to foal successfully. 

Map of major zebra highways

Model of terrain constructed from 3D point cloud

Fine-scale data collected from the collars show the preferred grazing area, drinking points and transit routes for zebra. In their dry season range, we found the zebra only drink once every 2-5 days and during the interim periods between drinking can travel up to 30km from the river. The data also allowed us to map out the major zebra 'highways' which form an extensive network. Analysing this network, we were able to show that zebra are capable of using multiple parallel tracks and can return to their course if perturbed from it with minimal disruption if progress to their intended destination can still be made. This has implications for the distribution of fences inside zebra home ranges in order to allow them to continue successful navigation of their landscape. 

Aerial Surveys of Hunting Environment

We flew UAVs with aerial survey cameras in the study area to collect a variety of different data. Each flight required the acquisition of approximately 300-600 individual aerial photographs, amounting to some 400GB of data. The drones were flown within sight at altitudes between 20 and 40m under manual control, with the operator controlling photo acquisition. 

Hunt routes were identified from GPS co-ordinates from collars and these sites were visited to mark out the area of interest. The drone was then deployed to survey the area by taking multiple overlapping photos which were then used to create models of the terrain. The previously collected hunt data from collars can be overlaid on the models to allow investigations into the effect of terrain and features on hunting dynamics, initiation and success.

Terrain mapping with the UAVs led us to investigate the herbivores' movements to research similarities and differences in drinking habits, how far they travel between watering holes and for how long. Typically, zebras appear to travel further than wildebeest in the monthly periods and are less likely to return to the same drinking hole. In contrast, wildebeest appear to travel in more cyclical patterns and congregate in smaller areas than zebra.

Muscle Physiology Investigations

In May 2016, the muscle physiology team from the RVC travelled to Botswana to undertake a muscle physiology study on herbivore muscle. Their objective was to characterise the contractile properties of intact muscle fibres to give a measure of heat output and work, and hence overall fibre efficiency. The follow on goal from this was to use these results to link events at a muscle level to whole animal energetics and efficiency. To achieve these ambitious aims, the team activated isolated muscles using various activation patterns (stimulus frequencies, shortening and lengthening rates and amplitudes) that mimic the in vitro movement patterns that the animals undergo during normal locomotion. 

To conduct these muscle studies, fine needle biopsies of locomotor muscles were taken from animals sedated for collaring and treated in the field to remove the muscle sheath so that only the contractile sheath remained. These were then taken to a lab set up at Tiaan's camp on the Boteti River. Over 11 days data were collected in day long experiments. A challenge for the team was ensuring a relatively seamless route for biopsies from animal to lab. The darting/collaring team had to start each day at dawn and then balance their own roles with the responsibility of collecting the biopsies and ensuring they remained attached at either end to aponeuroses and kept in oxygenated saline during transport back to the lab. An unexpected discovery was that small pieces of biopsy could be kept overnight for use the following day, a longevity in vitro unusual for a mammalian muscle. This gave the research team extra opportunity to explore the tissue physiology and meant there were a few days where the darting team could focus exclusively on their collaring, and not taking biopsies on top of that.

Tim West mounting muscle onto the thermopile 

Muscle bundle on thermopile

Measurements were carried out on a small muscle sample which was put on a rig that records the amount of mechanical work done through measurements of force and length and the amount of heat produced. This enables a direct measurement of efficiency at a muscle level that can be compared to habitat, ranging and ecological parameters such as the ability to survive without drinking, undertaking long migrations and living in hot and dry conditions. Experiments on UK rabbits were undertake to validate and demonstrate the measurements taken in Botswana (Skinned muscle fibres produce the same power and force as intact bundles from muscles of wild rabbits, Journal of Experimental Biology, NA Curtin, RA Diack, TG West, AM Wilson, RC Woledge, 2015).

Key outcomes of the data were quantification of muscle contraction costs in a typical muscle, and determination of the activation pattern where muscle power is most efficient. 

How much does a zebra drink?

A field visit was undertaken in October 2016 to temporarily install two force plate systems in the Makgadikgadi National Park. The plates were buried 0.5m under game trails that led to popular drinking points on the Boteti River and allowed us to weigh zebra before and after drinking in a non-intrusive manner. The force plate system consisted of two ATMI forceplates with a combined measurement area of 1800x600mm connected to a small, buried computer. The plates utilised an automatic trigger, which allowed them to weigh animals automatically as they walked over the plates whilst a camera recorded species, foot fall timings and the direction (to or from the river) of the animal’s movement. Game trail use was not affected by plate installation, with zebra and wildebeest happily walking over both the buried systems. Over a two week period 56 zebra were weighed by the force plate system. The plates will be deployed again in summer 2017 to increase the sample size and investigate seasonal effects. 

Installation of force plate system
Zebra crossing the force plates

Collaborations

Throughout our time in Botswana, we have had the opportunity to work alongside various local organisations and research groups to augment both our and their work. We collaborated with several local veterinary surgeons who aided with the darting and sedation of animals to be fitted with collars. 

Another of our collaborators, with whom we shared scientific discussion and who helped with cheetah collaring, was Cheetah Conservation Botswana (CCB). These incredible people are a driving force behind the efforts to sustain Botswana's population of cheetahs, the second largest in the world yet at only around 2,000 individuals, through scientific research, community outreach and conservation education. CCB also works with people, often in rural communities, affected by conflict with carnivores to promote coexistence. Their research into cheetah distribution, their habit preference, prey preference, and behaviour patterns helped inform our own work, while our partnership enabled them to apply collar data to their ongoing study into how cheetahs navigate and behave in their human-dominated landscape. 

We also worked alongside the Okavango Research Institute of the University of Botswana. The Okavango Delta is an area of particular interest due to its being one of the largest and most intact inland wetland ecosystems. Researchers from this institute are both studying and acting to conserve this area, and were involved in the deployment of collars on zebras and conduction of UAV field testing for vegetation survey and to film zebra locomotion. 

Elephants Without Borders is a charity dedicated to conserving wildlife and natural resources, using the African elephant as its ambassador. Through research and education they aim to motivate conservation efforts, create positive action for a harmonious future between mankind and nature, and prevent rural developments from infringing on conservation. Botswana has the largest elephant population in Africa, with the recovery of its population ironically leading to growing worry that they may have grown to greater numbers than the environment can sustain.This has caused significant increasing human-elephant conflict. Elephants Without Borders monitors the movements, status and behavior of wildlife to work towards securing key habitats and migratory corridors for wildlife and mankind to flourish together sustainably. We removed two VHF collars from wildebeest on their behalf and replaced them with GPS collars to minimise the number of researchers and vehicles entering the study area and the number of animals being darted. 

The Ann van Dyk Cheetah Centre has been invaluable in their assistance with collar development and testing under controlled conditions on their non-wild cheetahs. 

RVC Wildlife Tracking Collars

Early tracking collars

Lion with RVC tracking collar
Lion with RVC tracking collar

Simple animal tracking collars – incorporating a radio transmitter to allow the animal to be tracked using a radio receiver and directional antenna – have been used in wildlife research since the 1960’s. When the GPS navigation system was developed in the 1970’s the receivers required were initially far too large and power-hungry to be incorporated into an animal collar, but both size and power requirements were slowly reduced. This meant that for the last decade or so, it has been practical to incorporate a GPS receiver into a collar. At first, only a very few positions could be recorded per day because of the drain on the collar batteries, but over the last few years this has improved to multiple positions per day, allowing regular and accurate information on the animal’s location to be recorded without the need for continuous radio tracking.

But going beyond simple location recording towards measuring how the animal was actually moving second-by-second – the dynamics of how an animal moved and hunted – was still largely impractical. This required data from sensors such as high-quality accelerometers and gyroscopes – large, heavy and power-hungry devices – combined with continuous GPS data giving accurate positions several times per second. It simply couldn’t be done within the weight and battery limitations of an animal collar.

Advances in micro-electronics

Now, advances in electronics have changed all of that. A new class of accelerometers and gyroscopes has appeared based on “micro electro-mechanical system” (MEMS) devices, targeted at mobile phones, tablet computers, car airbag systems, and consumer devices such as the Nintendo Wii. By combining this new technology with the very latest high-performance GPS receivers and low-power computer chips and solar cell technology, it has become possible to create a wildlife collar that can capture fine-grained data on wild animal movement and behaviour in detail never before possible.

RVC Wildlife Collars

 

Cheetah wearing RVC tracking collar
Cheetah wearing a RVC tracking collar in Botswana.

The RVC Wildlife Collars incorporate a latest-generation GPS receiver, capable of producing up to five location fixes per second when required, but also capable of very low  power operation if only a few fixes per hour are required. This is combined with some of  the best available MEMS accelerometers and gyroscopes, allowing the animal’s movement  to be recorded at up to 300 times per second when required. To keep the battery  consumption as low as possible, a very low power central processing unit (CPU) is used to analyse the data from the accelerometer and change the way the collar is working  depending on the animal’s behaviour – for example by shutting down almost the entire collar circuitry when the animal is sleeping, but running all the sensors and GPS receiver  at full speed when a hunt is on.

 

A set of high-efficiency solar cells provide typically about a quarter of the collar’s power requirements, greatly extending the operating life of the collar before battery exhaustion.  A high-speed two-way radio transceiver on the collar allows the recorded data to be downloaded without disturbing the animal, and allows new settings and software to be uploaded to the collar as required.

 The RVC Wildlife Collars are species-specific and are designed and built by Alan Wilson and his team of electronics engineers. The collar is tailored to fit each animal  comfortably and safely and to collect data relevant to the particular study.



Triggering high speed data collection

The collar CPU is programmed to use the data from the accelerometer to control the other sensors and the GPS receiver, triggering them to start and stop data collection depending on the animal's activity level. This saves power and limits the potentially vast data files to a size that can be stored on the collar until the next upload.

The processed collar data can deliver the position, speed, acceleration, heading and track of the animal 300 times per second.

Tracking collars for BBC Horizon “The Secret Life of the Cat”

For the BBC Horizon programme “The Secret Life of the Cat”, the core technology from our Wildlife Collars – the GPS receiver, accelerometers, gyroscopes, CPU, and much of the associated software – was repackaged into a form that was small and light enough to be carried by a domestic cat. Core software functionality was retained, in particular the ability to change the collar’s operation and power consumption based on the cat’s behaviour, thus ensuring that the light-weight battery employed would still provide the required operating life.

Some of the domestic cat collars also carried a miniature high-definition video camera, which provided excellent video quality but only short recording time due to their limited battery life. To make best use of this finite recording time, the collars were programmed to only turn the camera on when the accelerometers indicated that the cat was active and the GPS receiver indicated that the cat was outdoors, thus maximising the amount of natural behaviour that was recorded.

Tracking collars featured in BBC One "Big Cats"

Our wildlife tracking collars made an appearance in Professor Alan Wilson's segment on the BBC One programme "Big Cats". Professor Wilson discussed his research into the locomotion dynamics of wild cheetahs as well as the technology developed at the RVC to collect data from free-ranging animals in the wild. 

Below is a list of the publications that have come from the LOCATE project. These papers or abstracts can be accessed by clicking on the title in the table below. 

Title Publication Year

Remarkable muscles, remarkable locomotion in desert-dwelling wildebeest

Nature

2018

Movement patterns and athletic performance of leopards in the Okavango Delta

Proceedings of the Royal Society B

2018

Biomechanics of predator–prey arms race in lion, zebra, cheetah and impala

Nature

2018

Cheetah Reunion - The Challenge of Finding Your Friends Again.

PLoS ONE

2016
Movement patterns of cheetahs in farmlands in Botswana. Biology Open 2016 2016
An exploratory clustering approach for extracting stride parameters from tracking collars on free ranging wild animals. Journal of Experimental Biology 2016
Improving the accuracy of estimates of animal path and travel distance using GPS drift-corrected dead reckoning.  Ecology and Evolution 2016
Determining position, velocity and acceleration of free-ranging animals with a low-cost unmanned aerial system. Journal of Experimental Biology 2016
Does wildlife resource selection accurately inform corridor conservation? Journal of Applied Ecology 2016
Adaptive opportunistic capture explains group hunting benefits in African wild dogs. Nature Communications 2016
Energy cost and return for hunting in African wild dogs and cheetahs. Nature Communications 2016
Skinned fibres produce the same power and force as intact fibre bundles from muscle of wild rabbits. The Journal of Experimental Biology 2015
Lessons from integrating behaviour and resource selection: activity-specific responses of African wild dogs to roads.  Animal Conservation 2015
Determining speed, track and acceleration of free running animals from a low cost UAV platform. Integrative and Comparative Biology 2015
Can dead reckoning techniques improve temporal resolution of measurements from tracking collars? Integrative and Comparative Biology 2015
Preferred speeds and gait classification in free ranging African Carnivores. Integrative and Comparative Biology 2015
Modern African wild dogs - Opportunists rather than Specialists. Integrative and Comparative Biology 2015
Optimal locomotion speeds in wild African carnivores during hunting and ranging. Integrative and Comparative Biology 2015
Muscle power in predator and prey species.  Integrative and Comparative Biology 2014

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