Baboons don’t play follow the leader – they’re democratic travellers

Robert John Young, University of Salford

Baboons in the wild are known for their highly strategic and hierarchical societies. So when it comes to decisions about where to go, one might expect that some bolshie individuals will direct the group through its habitat. However, a new study of the collective movements of wild olive baboons in Kenya suggests that there are more democratic processes at play.

For wild animals location is everything. The decision to head north instead of south may lead you to a fruiting tree, a pool with water or a place of shelter: all of these things could be the difference between life and death. For that reason, animal movements are never random. Even when searching for things, animals will use specific patterns of movements to sweep their environment. Social animal species like monkeys may not sit down and have a confab over a map, but they still need to make a decision about where the group should be heading.

A baboon in sheep’s clothing?

Numerous theoretical studies show the more you use collective information, the better the decision making process turns out. So it actually makes sense for clever animals like baboons to ignore a dominant individual no matter how much of a despot they are, but instead use a democratic process.

Oliver might be resourceful but look at that silly stroll. He clearly has no idea where he’s going.
Andicat/wikipedia

So far, there has been a limited amount of knowledge about how baboons make decisions about movements. The problem is how to study simultaneous and collective decision making in animals that live in large groups. Baboons typically live in groups of around 100. High accuracy GPS devices mounted on the majority of group members is the answer: this will reveal how animals coordinate their movements relative to one another. I have used this technique in the past on a much smaller scale to investigate the secretive lives of mated pairs of maned wolves in Brazil.

The researchers monitoring baboons in Kenya did just this. When an animal moved off, its influence on the other members of the group was observed. Did the other members follow (that is, did it “pull” them along)? Or did the other members resist the initiative to move off (that is, “anchor” the group). And what happened when several individuals moved off at the same time in different directions?

The researchers found that there was no relationship between position in the hierarchy and pulling the crowd along. In other words, top baboons were as likely to be followers as being followed. This illustrates that leadership and social roles within a social group can be distinct roles. Just because you are the leader does not mean that everyone else in the group treats you like you are infallible in your decision making.

In general individuals were followed when they moved purposefully off in a set direction and were able to rapidly recruit or “pull” other individuals in that direction. This makes sense in that it suggests to other group members that the moving individual’s behaviour is goal driven, for example by looking for food. Perhaps the individual has suddenly remembered the location of a fruiting tree. It would therefore appear that baboons like to follow the crowd – this is similar to quorum sensing behaviour in bees and ants when they are choosing a new nest. The option with the most votes wins.

The 90-degree rule

A big problem of group movement is how to resolve disagreement about the direction to be taken. It is rather like being lost in a strange city on a night out with a group of friends with widely differing opinions about where to go. One effect of this for both humans and baboons is that it delays any decision being made as the conflict is being resolved.

So what’s the solution? It turns out that baboons have a special rule. When the difference between two individuals trying to initiate movements in different directions is less than 90 degrees from one another, then it is resolved by splitting the difference and taking a middle path. However, if the difference of opinion about directions is greater than 90 degrees then individuals accept the choice of one individual over the other. Initiators of movement in a certain direction build up followers, and the individual that has accumulated most followers will end up determining the group’s direction.

You are wrong – the difference is 91 degrees, not 88. Let’s follow Jack.
Rod Waddington/wikimedia, CC BY-SA

It is surprising that something as important as group movement in baboons can be determined by a few simple rules, which are based on the idea that it is better to use the group’s collective knowledge than trust in the opinion of their leader. And perhaps even more so the fact that a dominant individual accepts that it is better to be a sheep than a shepherd in certain situations.

The Conversation

Robert John Young is Professor of Wildlife Conservation at University of Salford

This article was originally published on The Conversation. Read the original article.

The riddle behind zebra stripes

Brenda Larison, University of California, Berkeley

How the zebra got its stripes might at first seem like an esoteric question. But it has fascinated many generations and is embedded in the lore of Africa. It is also a question that offers a great educational tool by helping the general public understand how evolution shapes the variation we see in nature.

I began studying the question out of pure curiosity. But could it be more? Could the answer to why zebras are striped provide any benefits to society? There are many ideas about the advantages that stripes might confer on zebras.

Three ideas have some support: that stripes help zebra escape predation, avoid biting flies, and keeping cool. I’ll take up each of these ideas in turn, while speculating about the societal benefits that could obtain if they were proven to be true.

Predation and the dazzle effect

The most well-known idea about why zebras are striped is that they help them escape predation. The thought is that the dazzle effect of their stripes confuses the predator about either distance, speed, direction of movement, or where one zebra ends and the other begins.

The dazzle effect has already been put to use. In the first world war, ships were painted with bold black and white patterns in the hopes of making them less vulnerable to attack.

Research is mixed as to whether stripes actually lend such an advantage to zebras or might instead make them easier to catch. Once we understand whether stripes make something harder or easier to capture, rest assured that technology will make use of the fact.

Stripes as insect repellent

It has also been suggested that zebra stripes keep disease-carrying flies, such as tsetses and horseflies, from biting. Nagana, a form of sleeping sickness carried by tsetse flies, is a serious deterrent to livestock rearing in parts of Africa. Much research has gone into trying to mitigate this problem.

Researchers are working on not only why zebras are striped, but how. By trying to work out the genetic basis, we might one day be able to breed zebra-striped livestock. I can just see a herd of zebra striped cows contentedly munching away in a swarm of confused tsetse flies.

This solution for livestock would be a double-edged sword, though. The inability to rear livestock is one reason some areas of Africa are safe from human encroachment and are left for wildlife.

At any rate, the waterbuck may have already stolen the zebra’s thunder. Researchers have discovered that waterbuck give off an odour that deters tsetse flies. Collars exuding this smell are now being developed for livestock to wear. This is very much like your dog or cat wearing a flea collar.

Stripes to stay cool

There is another idea about the function of zebra stripes that could have an impact on their survival, and could possibly benefit humans and the rest of the planet. Collaborators and I recently discovered that the strength of striping in one species of zebra, the widespread plains zebra, varies with temperature.

The more stripy zebra are found in hot, tropical climates. Preliminary experiments also suggest that strong black and white stripes may help keep zebras cool under the tropical sun.

Zebra stripes differ.
Brenda Larison

If the biting fly hypothesis is true, temperature may also influence how many parasites they carry. Clearly this matters for zebra in the face of climate change. Zebra in regions of Africa that have seasonally cooler temperatures have subtler striping and often lack stripes on the legs.

Should climate change render these regions hotter, these less stripy zebras may have insufficient ability to thermoregulate and they may be subject to bites by flies that now harbour more parasites. Either of these could pose serious problems for zebras if their populations cannot evolve stronger striping quickly enough.

On a more positive note, if zebra stripes can truly create cooling, imagine an inexpensive cooling system for buildings that requires no energy input once in place. Instead of turning on the air conditioning, just roll out a black and white striped cover onto your roof during hot spells. This could significantly reduce energy usage and help mitigate climate change.

Only time will tell whether any of these ideas pan out. Meanwhile, I work simply to satisfy my curiosity, and hopefully yours.

The Conversation

Brenda Larison is Assistant Adjunct Professor, Department of Ecology and Evolutionary Biology at University of California, Berkeley

This article was originally published on The Conversation. Read the original article.

Pottoka Piornal ponies WE

This entry was contributed to Wild Equus by Lucy Rees, member and researcher of the Wild Equus Network (WEN). You can visit the Pottokas en Piornal website, where you will find more details about her work with the feral pottoka ponies.


Species: Equus caballus

Subspecies/Breed/Type: Pottoka (Basque Pony)

Country: Spain

Region/Province/Range: Sierra de Tormantos, Piornal (Extremadura-Caceres)

Population type: Feral

Management Authority:  Pottokas en Piornal

Estimated Population size: about 40 horses (2015)

Census August 2015

Foals 2015 m 5 (+ 1 that died) f 3

Yearlings    m 4 (b, 3n) f. 3  (d, 2n)

2 y-olds      m 1 (b)  f  4

3 & above   m 5 (b, 4s) f  15

Total 40, m 15, f 25
b= bachelor, s=stallion, n= still with natal band, d=dispersed  – 9/15 mares foaled. = 60%.

Of the 6 that did not foal, 4 were 3 y-o that foaled last year at 2, 1 is 3 y-o,  1 unknown (mare not seen for 3 months)


Details of Population

1200ha. of mountain between 700m and 1500m. , with two deep gorges. Lower-lying areas are oak wood (about 400ha) with scattered chestnut plantations, the latter mainly unavailable to the ponies. The rest is mainly high, dense heather, Spanish broom, bracken and rock, with occasional areas of grass.

Average winter temperature 2.8º; snow may cover areas over 1000m for up to a month. Average summer temperature 20.8º . Water is abundant except in dry summers when all but two springs may dry up. The ponies practice seasonal vertical migration.

The area may also be grazed by up to 600 goats. Occasional red deer, groups of fallow deer, wild boar, fox, martin, jineta, rabbits (few), walkers and cyclists share the area. No large predators.

The population was set up as an open-access study facility for equine researchers and students with non-invasive projects. All ponies can be identified individually and their life history is known. Pottokas are Basque ponies whose DNA variation corresponds to a wild, not domesticated breed. Ours have no management except culling to limit numbers.

Their social organization corresponds to other older feral populations: natal bands, home ranges (around 300ha.), natal dispersal, bachelor bands often joined by dispersing fillies. Three have tamed themselves but the rest cannot be touched although they admit close observation.

Population growth has been limited by culling. In 2014 one entire band (young stallion, old mare, her daughter and grand-daughter) were removed. In 2015 11 ponies (3 y-o stallion, 7 y-o mare, her yearling son, and 7 fillies of 1 and 2 years old were removed). The individuals were chosen to minimize social disruption, being mostly fillies in natal dispersal. To reduce possible conflicts each band was rounded up separately and the youngsters removed.

Despite apparent lack of good forage the ponies are in extremely good condition although lactating mares lose weight at the end of the summer. The ponies show an astonishing ability to self-heal even severe wounds. Parasite burden is negligible.

Structure and demographics

4 single-stallion natal bands, one bachelor band.
The population was set up in 2007/8 in Catalonia with two bands each of one stallion and three mares. On moving the population to its present location in 2011, a 3 year-old unrelated stallion was introduced.

Of the 11 foals conceived in Catalonia 9 were female. In Extremadura 20 colts and 19 fillies have been born.
Mortality:
12 y-o mare, piroplasmosis (Catalonia, 2007)
colt 6 months killed by hippies (c, 2008)
14 y-o stallion, infection from broken tooth (Extremadura, 2014)
12 y-o mare, herbicide poisoning (Extremadura, 2013)
yearling colt, eating plastic bag (E, 2014)
foal 3 weeks (E. 2015)
2 disappeared colts.

About half the fillies become pregnant as yearlings, giving a very fast-growing, female-skewed  population (see culling, below). Fillies that foal at 2 do not foal at 3. Colts begin (inefficiently) to form natal bands at 3 years old.

Issues worth noting and needed actions

a) Legal imperative to microchip, which causes stress and social disruption and is extremely difficult in practice. The European regulations allow exemption in wild or feral ponies but the Extremadura authorities do no recognize this.
b) Damage to fences and walls caused by herds of goats, whose owner refuses to use the gates, cause escapes, social disruption and conflicts with the police.

Bibliography and further reading

Genetic analysis in the basque pony-pottoka breed. Preliminary results

Genetic variability in two spanish horse populations: Preliminary results

Pottoka’s behaviour and training

El caballo al final de la última glaciación en el período postglacial

Hippo gets zebra foal across the river

A cool little video of how a zebra foal drifting away during a Mara River crossing manages to get to shore with the help of a female hippo.
Many tourists visit the Mara River crossings every year, in hopes of witnessing one of the most spectacular and popular animal migrations known. Images portraying the ‘red in tooth and claw’ struggle of Wildebeest and Zebra to get to better grazing grounds abound.
Incidents like these are still few and scattered, but are always a breath of fresh air.
An image of the heroine hippo and the zebra foal on shore.
Incidentally, the same hippo was reported to have helped a Wildebeest calf in a similar incident, only 10 minutes before.
African wildlife - Mother hippo rescues a baby wildebeest in Kenya
Image taken by the Sanctuary Olonana Camp Manager

Read more about these sightings here:

The social life of feral horses

“Understanding the social structure and organization of animals helps us better define a class of ecological relationships, including those of con-specifics living together.  Description of these relationships is complex and challenging, and analysis of patterns of relationships between individuals of a population a laborious one, entailing extended periods of observation.

Following the work of Rowell (1972); van Schaik & van Hooff (1983), a social structure is considered the composition of a particular group, as well as, the spatial patterns amongst individuals. How a social structure is organized will depend primarily on social interactions exhibited by different group members towards one another, setting the scene within which intra-specific communication takes place, and may include competition, cooperation or even dominant behavior in the acquisition of resources. A resource is an object, substance or energy source required for normal body maintenance, growth, and reproduction (Ricklefs, 1979; Wittenberger, 1981). “Resources are what an organism perceives as life necessities, e.g., food, mating partner, or a patch of territory. What an animal perceives to be its resources depends on both the species and the individual; it is the result of evolutionary processes and the history of the individual.” (Abrantes, 2011)

“The evolution of sociality among animals reflects a balance between the advantages and disadvantages of living in close proximity to conspecifics” (Krebs & Davies, 1993)

Feral horses, Equus caballus or Equus ferus caballus (depending on your inclination),  found in such disparate geographical locations as the Red Desert of Wyoming, the Great Basin of Nevada, the New Forest, or Assateague, have revealed much in the quest for deriving a general social framework for horses. Studies of these horses have revealed many similarities in the modus vivendi of the populations under scrutiny. However we must remember that similarity does not equate to sameness, and we should expect variations in phenotypic expression in relation to a dynamic and changing environment. The social organization of any given species from one region of its geographic range does not necessarily permit us to assume that other populations in different ecological settings, would display the same kind of social organizations (Banks, 1977).

According to Wilson (1975), a group is “[…] a set of organisms belonging to the same species that remain together for any period of time while interacting with one another to a much greater degree than with other con-specific organisms.

Horses basically have two categories of social organization, permanent groups and temporary assemblages (Rubinstein, 1981). These categories will obviously vary as a direct outcome of ecological pressures, mainly but not limited to food, water, predation and reproductive strivings. 

Living in herds provides advantages regarding fitness primarily in relation to avoidance of predators and potential threats through increased vigilance, as many eyes are better than few. Grazers, like horses, must interrupt their feeding for predator detection, lifting their heads to scan for possible danger at the slightest novel stimulus. With companions on the lookout, however, a single animal does not have to interrupt feeding as often and thus maximizes foraging time as well.  Advantages are magnified as living in groups provides ready access to animals of the opposite sex.

Variation in group size will also vary as a result of these ecological pressures. Larger groups deplete food patches quicker (i.e., more mouths to feed) and consequently must travel further to forage. When the travel costs associated with the increase in group size becomes prohibitive (more costly than beneficial), smaller groups are likely to become advantageous.

Geometry of the selfish herd – William Hamilton pointed out that if predators only take one prey at a time during an attack, the best strategy for a prey species would be to keep another individual between oneself and the predator or predators. Furthermore, his paper showed “[…] that even in non-gregarious species, selection is likely to favor individuals who stay close to others”. (Hamilton, 1970)

Most feral horse populations live in groups that inhabit large, overlapping home ranges. A home range is an area within which a horse restricts its activities seeks shelter, food and potential mates (Berger, 1986). More than just a space within which an animal lives and reproduces: a home range is an area where the animal can become intimate with its surroundings (Wittenberger, 1981).

A home range is not exclusive of other groups nor is it typically defended as a territory (Slater, 1999). Home range is, therefore, a descriptive term used to describe the area which an animal occupies during an annual season or a part thereof, “[…] without suggesting the particular means by which the space is maintained”. (Marler & Hamilton, 1966)

Home ranges contain preferential central core areas which vary greatly in size and shape. These areas are those in which horses spend a greater amount of time than others (Linklater et al., 2000). Berger found in his study(1986) that “[…] the defense of core areas or any other geographical region was not observed, and no places were exclusively used”. Furthermore, territoriality in the classical sense was not observed in any of the populations of feral horses studied but one (Welsh, 1975; Feist & McCullough, 1976; Keiper, 1976; Berger, 1986; Miller & Deniston, 1979).

Horses in the Shackelford Banks islands, off the American east coast, where found to defend territories (Rubinstein, 1981), “[…] possibly, due to the abundance of water and other resources which afforded for this strategy”. Instead of finding typical harem or multi-male bands, in overlapping home ranges, “[…], it was found that horses did not even live in fixed membership groups” (Rubinstein, 1981). Stallions were found to form territories that run along the width of the narrowest part of the island where visibility was not restricted, and necessary vegetation was readily available. Territories are areas occupied more or less exclusively by an animal or a group of animals by means of repulsion through overt defense or advertisement (Wilson, 1975).

W. M. Wheeler (1930) believed that the development of the family in addition to a highly developed neuromuscular system is essential to the formation of animal societies. A family is a reproductive unit, so long as its members remain together, it is, in fact, a rudimentary form of society with clear protective, nutritive and reproductive functions, as well as a division of labor in its components.

Although the harem type of structure has been understood as the basic structure of horse society, multi-male stallion bands are more common than one is often led to think. Bands consist of 1-26 mares and their offspring, accompanied by one or more stallions. Up to half the bands in a herd may contain more than one and as many as five stallions (Linklater et al., 1999). The population studied by Berger (1983; 1986) showed that bands found to last over seven months were mainly harem formations (88%) and the rest multi-stallion bands (12%). Miller (1981) found the same general pattern in his study of the Red Desert horses of Wyoming.

Family bands are stable social units. Stallion tenure averaged 2.11 years for twenty-four stallions in the Granite Range (Berger, 1983) but lasted as long as ten years on Sable Island (Welsh, 1975) and on Assateague Island (Keiper, 1985). The composition of adult mares in the band is also stable, with some mares remaining in the same band for life. In the Pryor Mountains of Montana, for example, only 7.6% of adult mares changed bands in a year (Feist and McCullough, 1975).

Natal bands are those into which an individual is born. (Keiper, 1985). Most young animals, male, female or both disperse from their natal bands, leaving the group in which they were born as maturity approaches.

Young males, sons, eventually leave their natal bands between 1-3 years of age, although it has been noted to occur earlier in orphaned foals and an account was described by Keiper (1985) of one Assateague pony foal who remained in his natal band to the age of four.

Most of these dispersed individuals form or join bachelor groups. Bachelor groups are comprised of males that do not form breeding units, either because they cannot obtain or maintain females. These bachelor bands can be made up of between 2 – 18 individuals, Joel Berger found a median group size in his studies of four in mid-spring (Berger, 1986).

Klingel (1975) considered bands found within herds as adaptations to seasonally changing ecological conditions. As the stallion defends his mares rather than territory, the band is not restricted in its movements so it can make use of the best available food from season to season.

It has been speculated by Hoffman (1983) that a population in central Australia where no such organization was found may be an exception to the rule. Following this report, Berger (1986) hypothesized that “where xeric conditions prevail, it seems logical to expect that the band structure would break down because of presumed difficulties males would have in maintaining harems and still meeting the constant stresses associated with water demands.”

 

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