Hyena Scent Posts Use Symbiotic Microbe Messengers

Twitter limits human communication to a mere 140 characters. Animals’ scent posts may be equally as short, relatively speaking, yet they convey an encyclopedia of information about the animals that left them.

In the current issue of the
Proceedings of the National Academy of Sciences, a Michigan State University researcher shows that the detailed scent posts of hyenas (Figure 1) are, in part, products of symbiotic bacteria, microbes that have a mutually beneficial relationship with their hosts.

“When hyenas leave paste deposits on grass, the sour-smelling signals relay reams of information for other animals to read,” said Kevin Theis, the paper’s lead author and MSU postdoctoral researcher. “Hyenas can leave a quick, detailed message and go. It’s like a bulletin board of who’s around and how they’re doing.”

hyena-scent-communication_lg
Figure 1. A spotted hyena scent marking. (courtesy of Michigan State University)

Interestingly, it is the bacteria in pastes – more diverse than scientists had imagined – that appear to be doing the yeoman’s job of sending these messages.

“Scent posts are bulletin boards, pastes are business cards, and bacteria are the ink, shaped into letters and words that provide information about the paster to the boards’ visitors,” Theis said. “Without the ink, there is potentially just a board of blank uninformative cards.”

Theis, who co-authored the study with
Kay Holekamp, MSU zoologist, studied multiple groups of male and female spotted hyenas and striped hyenas in Kenya.

By using molecular surveys, they were afforded unprecedented views of the diversity of microbes inhabiting mammals’ scent glands. The researchers were able to show that the diversity of odor-producing bacteria in spotted hyena scent glands is much greater than historical studies of mammals had suggested (Figure 2).


scentpost
Figure 2. Variation in the bacterial communities and volatile fatty acid (VFA) profiles of the pastes of immigrant male, lactating female, and pregnant female spotted hyenas in the Talek clan. (A and C) A plot showing variation in the structure of paste bacterial communities among Talek clan members. (B) A heat map of the mean abundances of the prominent bacteria in the pastes of Talek hyenas. (D) A heat map of the mean percent abundances of VFAs in the pastes of Talek hyenas. From Theis et al. 2013)

The diversity, however, still consistently varies between hyena species, and with sex and reproductive state among spotted hyenas, Theis added. Importantly, the variation in scent gland bacterial communities was strongly correlated with variation in the glands’ odor profiles, suggesting that bacteria were responsible for the variation in scent.

For the current paper, Theis’ team was the first to combine microbial surveys and complementary odor data from wild animals. The studies’ findings leave Theis anxious to return to the field.

“Now I just need to get back into the field to test new predictions generated by this study,” Theis said. “The next phase of this research will be to manipulate the bacterial communities in hyenas’ scent glands to test if their odors change in predictable ways.”


Source: Modified from materials provided by Michigan State University.

Reference

Theis KR, Venkataraman A, Dycus JA, Koonter KD, Schmitt-Matzen EN, Wagner AP, Holekamp KE, & Schmidt TM (2013). Symbiotic bacteria appear to mediate hyena social odors. Proceedings of the National Academy of Sciences of the United States of America PMID: 24218592


How Cheetah Really Hunt

Researchers at the Royal Veterinary College have captured the first detailed information on the hunting dynamics of the wild cheetah (Acinonyx jubatus) in its natural habitat. Using an innovative GPS and motion sensing collar they designed, Professor Alan Wilson and his team were able to record remarkable speeds of up to 58mph.

To date, measurements of cheetah locomotion mechanics have only been made on captive animals chasing a lure in a straight line, with few studies eliciting speeds faster than racing greyhounds. For wild cheetahs, estimates of speed have only ever been made from direct observation or film, in open habitat and during daylight hours.

Wilson’s team developed a tracking collar
equipped with a GPS module and accelerometers, magnetometers, gyroscopes. These sensors recorded precise position and velocity data of the animal’s movements.

Collar software monitored the accelerometers creating activity summaries for each brief hunting event. Overall, researchers recorded data from 367 runs by three female and two male adult cheetahs over 17 months (Figure 1).

cheetah

Figure 1. A cheetah wearing a GPS collar makes a sharp turn (From Wilson et al, 2013)

Data revealed that wild cheetah runs started with a period of acceleration, either from stationary or slow movement (presumably stalking) up to high speed. The cheetahs then decelerated and maneuvered before prey capture. About one-third of runs involved more than one period of sustained acceleration. In successful hunts, there was often a burst of acceleration after the speed returned to zero, indicating that the cheetah was subduing the prey – in this case mainly Impala, which made up 75% of their diet.

The average run distance was 173m. The longest runs recorded by each cheetah ranged from 407 to 559 m and the mean run frequency was 1.3 times per day, so, even if some hunts were missed, high speed locomotion only accounted for a small fraction of the 6,040-m average daily total distance covered by the cheetahs (Figure 2).

cheetah1

Figure 2. Some of the hunt statistics from the study. a, Top speed, averaged over a stride, reached in each run color-coded for outcome. b, Distance covered in each run. c, Top speed in each run coded for terrain type. d, Peak acceleration and deceleration recorded in each run. (From
Wilson et al. 2013)

The team was also able to identify factors that make up a successful hunt. Successful hunts involved greater deceleration on average, but there was no significant difference in peak acceleration, distance travelled, number of turns, or total turn angle. Rather, outcome was determined in the final stages of a hunt (rather than hunts being abandoned early to save energy or reduce risk of injury), and the higher deceleration values likely reflect prey captures.

The acceleration power for the cheetahs was double that for racing greyhounds and more than three times higher than polo horses in competition. Interestingly, grip and maneuverability, rather than top speed, were shown to be key to hunting success. Hunts involved considerable maneuvering, with maximum lateral (centripetal) accelerations often exceeding 13ms
-2 at speeds less than 17ms-1 (polo horses achieve 6ms-2).

According to Professor Alan Wilson, “Although the cheetah is recognized as the fastest land animal, very little is known about other aspects of its notable athleticism, particularly when hunting in the wild. Our technology allowed us to capture what to our knowledge is the first detailed locomotor information on the hunting dynamics of a large cursorial predator in its natural habitat and as a result we were able to record some of the highest measured values for lateral and forward acceleration, deceleration and body mass.

Source: Modified from materials provided by the Royal Veterinary College, London.


Reference
Wilson, A. M., J. C. Lowe, K. Roskilly, P. E. Hudson, K. A. Golabek & J. W. McNutt (2013). Locomotion dynamics of hunting in wild cheetahs Nature DOI: 10.1038/nature12295


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wild_dogs1
Figure 2. A bar chart showing the mean time to retreat by wild dog packs’ in response to lion roars in habitats of differing density. (Webster et al., 2012)

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wild_dogs2
Figure 3. Wheel diagrams showing the direction and distance travelled by wild dog packs in the hour following playbacks of lion roars or hyena whoops. The playback loudspeaker is located 100 m north of this center point. (From Webster et al., 2012)

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References

Webster, H., McNutt, J., & McComb, K. (2012). African Wild Dogs as a Fugitive Species: Playback Experiments Investigate How Wild Dogs Respond to their Major Competitors Ethology, 118 (2), 147-156 DOI: 10.1111/j.1439-0310.2011.01992.x
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