Affiliative (af)

A review of literature on the social behaviour of horses is likely to lead many to think equine society is governed solely by the establishment of social hierarchies, usually based on the outcomes of social conflict or competition, commonly referred to as agonistic behaviour.

The description of animal societies is mainly based on agonistic classifications, in which cooperation and affiliative behaviour were overshadowed by the competition-aggression-reconciliation paradigm generally emphasized by many writers.

Affiliative interactions [af] refer to the activities between two or more (dyadic, triadic, poliadic) individuals within a social group with the function of developing, maintaining or enhancing social bonds. {Equus Ethogram Project}

Affiliative is from Medieval Latin; affiliatus, past participle of affiliare to adopt as a son, from Latin ad- + filius son

konik stallions mutual grooming

Indeed, agonistic and affiliative behaviour are inextricably intertwined (Price & Sloman, 1993) in the complexity of social interactions, making it a laborious task to filter away the units of behaviour neatly into separate compartments for either one type of interaction, or the other.

Social interactions lay on a behavioural continuum, a continuous stream of movements  (Fentress, 1990; MacNulty et al, 2007) or spectrums of behavior (Abrantes, 2011):

“The distinction between any two behaviour is a matter of function; the borderline separating one category from the other is a matter of observational skill, contextual parameters and convention; the way we understand it all is a matter of definition.” (Abrantes, 2011)

For instance, in the ‘Agonistic ethogram of the equid bachelor band’ published by McDonnell & Haviland (1994), agonistic encounters were considered based on their intensity, running or flowing across a spectrum from “very quiet affiliative behaviour to serious aggression” (McDonnell & Haviland, 1994).

In this Equus Ethogram Project, affiliative interactions will be classified separately from agonistic ones, at least when at all possible. A host of authors have extracted units of agonistic behaviours from the interwoven fabric of equine social interactions, so it should be likewise possible to extract those other units of behaviour which promote group cohesion: affiliative behaviours.

DSC03382

The results of a growing body of research on free-living mammals suggests that affiliative social interactions, those enhancing social bonds, have important fitness consequences for individuals ( Swedell, 2002; Weidt et al, 2007; Silk et al. 2003, 2010; Cameron et al. 2009; Frere et al. 2010; Wey & Blumstein 2012) engaged in them.

In horses as in most social mammals, affiliative interactions are usually described by mutual grooming, play and group resting. This ethogram considers including more subtle forms of affiliative behaviour, such as the frequency or duration one individual is found sharing close proximity with others as an indication of their level of bonding (Hinde 1976; Garai 1992; Kleindorfer &Wasser 2004).

This Equus Ethogram Project is an on-going work, and the general framework, or particular sections and pages will be updated as new light is shed or brought to our knowledge.

Social Interactions (Si)

The importance of sociality to horses, Equus (ferus) caballus, is a topic that can never be emphasized strongly enough, their survival strategies and reproductive successes are highly dependent on the formation of cohesive social bonds (van Dierendonck, 2006 ). In fact, horses should not in my opinion be considered in any other context than a social one.

Tremendous effort has gone to describe the “workings” of the horse, how they behave and live, but many fail to see that living in close proximity with a con-specific has been shaped by millions of years of natural selection.

Despite millennia of domestication horses that have either been set free or have escaped and allowed to roam on their own accord, have in many parts of the world:  thrived by adopting survival and reproductive strategies that are generally quite similar to one another.

The fundamental similarities unveiled by years of descriptive studies are a testament to their evolutionary importance. But, similarities do not equate to sameness and differences found in their ways of life are likely to shed light on alternative life strategies, and their incredible biological plasticity which allows them to “fit” into such distinct environments.

It may be dead obvious to most that all extinct and extant equids are in fact horses. Equus, the name Linnaeus (1758) used to classify the genus that included the zebras, half-asses, donkeys, Przewalski and caballus, is a Latin name meaning: horse.

Throughout this Ethogram, emphasis is on Equus caballus, and use of the colloquial term “horse” is a shorthand referring exclusively to this species.

Studies of social behaviour are in fact studies of “(…) cooperation between individuals” (Tinbergen, 1953), and cooperation will be the centerpiece of our approximation to the social life of Equus caballus throughout this present work.

Just as organisms are communities of parts, so too societies are communities of individuals wherein cooperation, mating and the rearing of young play a vital role and in which individuals are driven by conflicting needs and interests. In other words, animal societies are characterized by cooperative and conflictive interactions among individuals: those between nearby con-specifics. (Whitehead, 2009)

It makes sense to consider that sociality brings about both ecological and genetic benefits to individuals by allowing them to better acquire and use certain resources, but group living has inherent costs too:

Increased foraging efficiency, improved predator detection, avoidance and defense, as well as easier access to reproductive options are three of the more important benefits of group living.

At the same time group living is likely to heighten competition for resources, aggression among group members, as well as increase exposure to parasites and disease. (Alexander, 1974) For social behaviour to be adaptive, advantages must outweigh the costs associated with group living (Alexander 1974; Wrangham & Rubenstein 1986).

Animals that live together influence each other in a myriad of ways, and serve a number of functions. In horse societies all individuals associate with all other individuals at some rate and any resulting order is related to the ecology of a population, including interactions with con-specifics.

Included under the section of Social Interactions, you will find the following subcategories:

  • Affiliative interactions (af)
  • Agonistic interactions (ag)
  • Communication (C)
  • Play (P)
  • Sexual (sx)
  • Parental (par)
  • Bonds (bd)
  • Roles (rls)

Huddling (hd)

A huddle is characterized by individuals crowding or gathering together. Most often, huddles are linked to thermoregulatory processes, and this social thermoregulation, or “(…) the ability of some species to use sociality or grouping to regulate their body temperature” (Gilbert, 2010), is a common energy saving strategy for many endothermic species (Canals, 1998; Alberts, 1978).

By bunching together, individuals reduce the body surface area exposed to inclement weather, consequently reducing energy spent in regaining a conservative equilibrium (Humphreys, 1933), or homoeostases.

In terms of horses huddling as a means of social thermoregulation, there really is very little work done. During cold weather horses have been observed to huddle or crowd together, on windy or rainy days; horses typically stand close to one another with “backs to weather” or “backs to natural windbreak”, as described by McDonnell (2003):

Backs to weather – Typically observed during windy or rainy days, Two or more horses stand closely together with their “(…) hindquarters into the wind.” (from the Equid Ethogram p. 79)

Backs to natural windbreak – Two or more horses stand closely together with their “(…) hindquarters protected from the wind by vegetation or other feature of the environment.” (from the Equid Ethogram p. 78)

McDonnell (2003), suggests that the backs to weather behaviour reduces the body surface area exposed to inclement weather, thus minimizing heat loss; in short it serves a thermoregulatory function.

In horses, the social bonds between unrelated mares, friendships, contribute to reproductive success as suggested by Cameron et al (2009) in a study on the Kaimanawa feral horses of New Zealand.

Horses have preferred partners within their band or herd with whom they associate more often with than other members of the group. Claudia Feh (1987), found that in the Camargue horses, horses had up to two, rarely three, preferred partners. These affiliative interactions are characterized by individuals sharing “personal space” (Dierendonck & Goodwin, 1992), and synchronizing activities.

Despite huddles not being extensively studied in horses, it is frequently mentioned in equid related literature, especially regards to group rest (Tyler, 1972; McDonnell, 2003; Ransom & Cade, 2009), or social grooming such as in mutual insect control. (McDonnell, 2003; Ransom & Cade, 2009)

Before going any further, let’s differentiate two types of huddles, namely; tight huddles and loose ones (Behnke, 2012). Tight huddles are those in which the majority of group members are in physical contact with one another, or separated by < 50 cms, leaving no gaps between individuals (Behnke, 2012). In contrast, loose huddles are those in which the majority of group members are in close proximity; from > 50 cms to < 150 cms, but not in physical contact with one another. Both between individual distances are currently in use in the ongoing Equus Ethogram Project.

Whether horses are grouped tightly or loosely may seem trivial, but for the sake of alienating the functional characteristics of different huddles, and their forms, the distances between individuals is likely of prime importance.

In tightly huddled horses, insect control is facilitated between group members. (Ransom & Cade, 2009) Several studies suggest that animals tend to group together when biting fly density or harassment is high (Bergerund, 1974; Schmidtmann and Valla, 1982; Rutberg, 1987; Rubenstein and Hohmann, 1989).

In the warmer months, which tend to correlate with an increase in insect harassment, two or more horses stand close together, typically tail to shoulder to the nearest neighbour. This is usually referred to as anti-parallel standing. In this position, individuals take advantage of one’s proximity to another to keep pesky biting insects at bay. Typically, horses have flies swished from their faces by the tail of a neighbour, but this can also be achieved by rubbing or bumping those close by.

Ingestive Behaviour (ing)

Under this heading we have classified behaviours related with taking material through the mouth and into the digestive system.

Horses are an herbivorous, grazing species that graze an average of 14-15 hours a day in the wild. Ronald Keiper (1985) found that horses on Assateague island spent 78% of daylight hours grazing. Horses are non-ruminants; they have a single stomach and the digestion of ingested roughage occurs in the cecum at the end of the large intestine. Cecal digestion, high level of food intake, and quick passage of food through the digestive system allows horses to have a diet high in fiber and low in protein.

Although horses prefer grasses (McDonnell, 2003), they are known to forage and derive nutrition from bark, tree, shrub buds, small woody stems, aquatic plants, fruits, roots and seeds (Hubbard and Hansen 1976; Varva and Sneva 1978; Salter 1978; Salter and Hudson 1979; Hanley and Hanley 1982; Krysl et al. 1984a). Feral and free ranging horses also pick food from the floor, and have been noted to glean and lick as well.

On Assateague Island along the Maryland-Virginia coast Keiper  (1985), found that these horses graze during 54.6% of the night time hours. Tyler (1972) in her 3 year study of the New Forest ponies stated; ‘from the few observations that were made at night, it seemed that most of the hours of darkness in all seasons were spent feeding’. From these studies it seems that on the onset of darkness walking and drinking activity becomes greater, especially in the first hours of darkness (Keiper, 1985).

Drinking in feral horses is not as frequent as one would expect, many only drink once or twice a day and some have been noted to travel considerable distances to drink once every 2 days. Drinking activity is variable in time and frequency and occurs both during day and night. (Pellegrini, 1971; Feist & McCullough, 1976) A direct correlation was observed between drinking frequency and ambient temperatures, with a clear increase in frequency occurring at temperatures above 30 C. (Crowell-Davis, 1985)

The category Ingestive Behaviour includes the following:

  • Suckling (sk)
  • Grazing (G)
  • Browsing (B)
  • Drinking (D)
  • Gleaning (gl)
  • Picking (pk)
  • Pica (Pc)
  • Corpography (cv)

Rest (Re)

Horses rest either standing or lying on the ground, and up to 30% of horse’s time budget can be spent resting. Rest in horses is generally a social and socially facilitated enterprise (see Group Rest), when one horse rests, others group members rest. Typically, in close proximity to other group members (Tyler, 1972; Feist & McCullough, 1976; Kimura, 1998; Sigurjonsdottir, 2003; Heitor et al, 2006), either in tight groups, or alternately, in groups of one or two pairs (Feist & McCullough, 1976).

However, foals were observed to rest together even though their mother’s were from different bands (Tyler, 1972).

Tyler (1972) observed seasonally different mean resting times in the New Forest ponies in her study. In winter daylight hours, adult ponies were observed to have 2-3 resting bouts lasting a mean length of about 40 minutes. Foals rested a little bit longer, about 44 minutes (Tyler, 1972). In summer, the length of resting bouts increased.

Not only did resting bouts increase in duration during the summer months, but New Forest ponies sought shelter in ‘shades’ (Tyler, 1972) for up to 5 hours.

Affiliative behavior in Equus caballus

Introduction

A review of literature on the social behavior of horses is likely to lead many to think equine society is governed solely by the establishment of social hierarchies, usually based on the outcomes of social conflict or competition, commonly referred to as agonistic behavior.

Agonistic interactions are social activities “related to fighting, whether aggression or conciliation and retreat.” (Wilson, 1975)

“Behavior patterns associated with fighting and retreat, such as attack, escape, threat, defense and appeasement.” (Slater, 1999)

The description of animal societies is mainly based on agonistic classifications, in which cooperation and affiliative behaviors were overshadowed by the competition-aggression-reconciliation paradigm generally emphasized by many writers.

Affiliative interactions refer to the activities between two or more (dyadic, triadic and so on) individuals within a social group with the function of developing, maintaining or enhancing social bonds. {Equus Ethogram Project}

konik stallions mutual grooming

Indeed, agonistic and affiliative behavior are inextricably intertwined (Price & Sloman, 1993) in the complexity of social interactions, making it a laborious task to filter away the units of behavior neatly into separate compartments for either one type of interaction, or the other.

Social interactions lay on a behavioral continuum, a continuous stream of movements  (Fentress, 1990; MacNulty et al, 2007) or spectrums of behavior (Abrantes, 2011):

“The distinction between any two behaviors is a matter of function; the borderline separating one category from the other is a matter of observational skill, contextual parameters and convention; the way we understand it all is a matter of definition.” (Abrantes, 2011)

For instance, in the ‘Agonistic ethogram of the equid bachelor band’ published by McDonnell & Haviland (1994), agonistic encounters were considered based on their intensity, running or flowing across a spectrum from “very quiet affiliative behavior to serious aggression” (McDonnell & Haviland, 1994).

In this Equus Ethogram Project, affiliative interactions will be classified separately from agonistic ones, at least when at all possible. A host of authors have extracted units of agonistic behaviors from the interwoven fabric of equine social interactions, so it should be likewise possible to extract those other units of behavior which promote group cohesion: affiliative behaviors.

DSC03382

The results of a growing body of research on free-living mammals suggests that affiliative social interactions, those enhancing social bonds, have important fitness consequences for individuals ( Swedell, 2002; Weidt et al, 2007; Silk et al. 2003, 2010; Cameron et al. 2009; Frere et al. 2010; Wey & Blumstein 2012) engaged in them.

In horses as in most social mammals, affiliative interactions are usually described by mutual grooming, play and group resting. This ethogram considers including more subtle forms of affiliative behavior, such as the frequency or duration one individual is found sharing close proximity with others as an indication of their level of bonding (Hinde 1976; Garai 1992; Kleindorfer &Wasser 2004).

This Equus Ethogram Project is an on-going work, and the general framework, or particular sections and pages will be updated as new light is shed or brought to our knowledge.

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