By Derek Lee, Wild Nature Institute

Highlights
•Home ranges of giraffes near populated towns were larger than those farther away.
•Dense human areas may force giraffes to range farther to obtain resources.
•No such negative relationship was evident with indigenous pastoralist homesteads.
•Rainfall explained 74% of the variation in giraffe home range size across Africa.
•Home ranges were smaller in regions with higher rainfall and greater productivity.

ARUSHA, Tanzania, 22 February 2019 – Giraffes are huge browsing animals that live in African savanna ecosystems where they must find everything they need to survive and reproduce in landscapes increasingly impacted by human activities. People are converting natural savannas to towns and farms, and cutting trees for fuelwood and charcoal industries, all of which potentially degrade giraffe habitat. The spatial area over which an animal repeatedly travels in search of food, water, shelter and mates is the home range, a concept used by ecologists to describe space use by animals. Home range behavior is an expression of an animal’s decision-making process about how to access the resources needed for survival and reproduction. A new study examining what affects the size of giraffe home ranges was published this week in the journal Animal Behaviour by an international team of wildlife researchers from University of Zürich, Penn State University, and Wild Nature Institute. The team found that giraffes living closer to towns had larger home ranges than giraffes living far from towns, suggesting a need to range longer distances—and expend more energy—to obtain critical resources in human-impacted areas. No such relationship was evident with bomas, which are homesteads built by indigenous livestock-keeping Maasai people, suggesting that giraffes are tolerant of more traditional, lower-impact land uses. “Giraffes are vulnerable to extinction after a 40% population decline during the past 3 decades,” said Mara Knüsel a graduate student at the University of Zürich and first author of the study. “Identifying factors affecting space use help wildlife conservationists to make better decisions for at-risk species such as giraffes.”

As one of the largest herbivores on earth, giraffes have a profound impact on plant populations, vegetation structure, and ecosystem processes where they live. Giraffes are also a favorite animal sought by ecotourists on safari in Tanzania, where the safari industry is the number-one dollar earner and the largest economic sector in the country. “Most studies that previously looked at home ranges of giraffes didn’t look for environmental factors that determine the observed home range size, so this study goes beyond the pattern to reveal the process behind it,” said Monica Bond, PhD candidate at University of Zürich and senior author of the study.

The team quantified home range sizes for 71 adult giraffes from data collected over 6 years, and examined correlations between individual home range sizes and environmental and anthropogenic factors in the spatially heterogeneous Tarangire Ecosystem of Tanzania, to better understand potential mechanisms driving space use of this threatened megaherbivore. They also compared home range estimates from published data for 8 giraffe populations across Africa, and examined the relationship between giraffe home range size and mean annual rainfall at the continental scale as a potential explanation for observed variation in space use among populations. Rainfall was negatively correlated with home range size and explained 74% of the variation in giraffe home range sizes across Africa. This relationship between rainfall and space use by a large herbivore is not surprising, given that rainfall is the main driver of vegetation productivity and thus food availability. Greater availability and access to critical resources such as food and water leads to smaller home range sizes. “Human disturbance and fragmentation of habitat in and around densely populated areas likely reduced the local forage and water resources available for giraffes, forcing individuals to increase their movements and use of space to obtain these resources,” said Knüsel. “Similarly, lower rainfall and lower primary productivity forces individuals to range more widely.”

The study at the publisher's site:
https://doi.org/10.1016/j.anbehav.2019.01.017

Giraffe are the tallest animal on earth, so naturally scientists have turned to big data solutions for giraffe conservation.  Researchers from Penn State and Wild Nature Institute are conducting one of the biggest large mammal studies ever undertaken by studying births, deaths, and movements of more than 3,000 giraffes across a 4,000 square kilometre landscape in the Tarangire Ecosystem of northern Tanzania, East Africa.

Dr. Derek E. Lee, Associate Research Professor at Penn State University’s Department of Biology and Principal Scientist of the Wild Nature Institute said, “These are big animals, and they cover big distances, so naturally we are using big data to learn where they are doing well, where they are not, and why, so we can protect and connect the areas important to giraffe conservation.”

Giraffe populations have declined precipitously across Africa due to habitat loss and illegal killing for meat. “We needed new tools to figure out how we can save giraffes, and there was a harmonic conjunction of technology that made our work possible,” said Lee.
Lee’s team uses digital photographs of each animal’s unique and unchanging spot patterns to identify them throughout their lives. However, the analysis process is very manually intensive and time-consuming. Many thousands of photos have to be processed per year, and for every photo the giraffe body in the image has to be manually cropped to provide just a giraffe torso to the pattern recognition software. To improve this process, Microsoft scientists have provided a new image processing service using machine learning technology deployed on the Microsoft Azure cloud.

Using a computer vision object detection algorithm, the Microsoft team trained a program to recognize giraffe torsos using some existing annotated giraffe photos. The program was iteratively improved using an efficient Active Learning process, where the system identified new images and showed its predicted cropping squares on these images to a human who could quickly verify or correct the results. These new images were then fed back into training algorithm to further update and improve the program.  The resulting system identifies the location of giraffe torsos in images with a very high accuracy. A description of the work was published this week in the journal Ecological Informatics.
The new system dramatically speeds up the important research being performed by the giraffe scientists. “It is wonderful how the Azure team automated this tedious aspect of our work,” said Lee. “It used to take us a week to manually process our new images after a survey, now it is done automatically in minutes!”

 Allonursing (or allosuckling) is when a mother nurses young that are not her own. It is rarely seen in wild giraffes. For example, Pratt and Anderson (1979) reported that out of 860 observations of nursing attempts in Serengeti National Park, just 37 were by an unrelated calf, and just one unrelated calf was successful in getting any milk. In Katavi National Park, Saito and Idani (2018) documented only 5 of 71 allonursing attempts were successful, These two previous studies of wild giraffe allonursing concluded that this phenomenon happens when the mother appears to be unaware that the nursing calf is not her own. Thus, the authors of these studies believe the instigator of allonursing is unrelated calves stealing milk from unwitting mothers.
However, in Wild Nature Institute's recent giraffe survey, we witnessed a remarkable case of simultaneous multiple-calf allonursing. We watched an adult female approach a group of calves, and 3 of the calves immediately ran over and began suckling from her. She allowed this nursing for well over a minute!  She appeared to be perfectly aware of the situation, and given that the calves rushed to her when they saw her, we suspect she has given her milk to these calves before.

Why did this happen? We have documented 82 extended nursing bouts (when a calf was observed to suckle for more than 10 seconds) during our 8 years of giraffe research in the Tarangire region, but this is the very first time we've seen more than one calf allowed to suckle - let alone 3 calves! Perhaps she lost her calf and still has milk that she is sharing with calves in her herd. Or, one of the nursing calves could be her own, but she is apparently allowing unrelated calves to also have her milk, so this does not appear to be milk theft.  A concern is that her own calf may be deprived of some of the milk it needs for rapid growth. Whatever the context, this was a rare and interesting instance of simultaneous multiple-calf allonursing. Giraffes continue to surprise us!

Have you observed allonursing?
Tell us about it.
#doublemothersucker