Horse Behavior Moira Ilg ERS April-2004

Outline Introduction and General Background Social Status or Ranking Foal and Mare Behavior Stallion Behavior Grazing Behavior Conclusions and Possible Implications

General Background Factors that influence dominance relationships Body size Physical condition Age Older the more dominant Sex Previous agonistic encounters Group size Dominance hierarchy of parents

Background continued Band structure Single adult male Adult females and their offspring Normally stable Changes are normally juvenile males and females Juvenile males may remain solitary for months or years Juvenile females normally bands A well defined hierarchy is present during grazing and will persist if they are provided with food

General Background Behaviors Threatening Behavior Maybe widespread or may have a few favorites to pick on Is often one sided If there is a “winner”, they move up in rank

Behaviors Grooming Normally groom with two or three individuals that are similar in rank and age

Behaviors continued Play Important for social development of young Most common within in peer groups Submissive Often a response to threatening behavior

Social Status or Ranking Top ranking individual Large number of threats Distributed widely across the herd Often don’t have “friends” Stallion Is often times the only breeding male Mare Often decreases aggressions as rank becomes higher

Social Status or Ranking Friends Normally close in age and social status Mares may bond more closely with those that are related to them It is important account for “friendships” when assessing the distribution of threats

Social Status or Ranking Tend to be selective about who they interact with Animals tend to spend the most time near individuals that have the same rank or age or both Top ranking animals are seldom seen alone or in a small group Elders are less social than the young Often have fewer interactions with younger subordinate mares

Social Status or Ranking May recognize individuals that they have competed with Leading to fewer competitions in older animals

Theories of the evolution of bonds Evolved between mares and stallion in a band because of pressure from predators that hunted cooperatively Protect mares against harassment from other stallions and reduce inter-mare aggression

Mares Acts of aggression is most common with mares that do not have foals The least amount of aggression is seen between mares that have foals Protection of foals

Mares Intermediate aggression is seen between mares that have foals and those that do not Young mares are much more aggressive than older mares when foals were less than a week old

Mares continued Older mares have fewer encounters of aggression Number of acts of aggression decrease as the mare becomes older Aggression frequencies increase in May (foaling season) Frequencies of aggression increase significantly the closer the mare is to parturition

The Advantage of Being A Dominant Mare Receive less aggression Access to shade on hot sunny or rainy days to rest Increased access to feed Supermare May suppress conception, induce abortions, or harass or kill offspring of subordinate mares However, dominant mares may not live as long They have increased amount of stress and a increased amount of cortisol

The Disadvantages of Being A Subordinate Mare Increased acts of aggression Denied access to shady areas Give birth to fewer or less fit foals Denied access to food Decreased growth rate

Foals Foals will often play with foals of their dam’s friends Also like to associate with foals of the same gender

Foals In the case of fillies they most often will have a similar rank to their dam Dams may assist their foals in agonistic encounters Foal-mare association Genetics

Stallion Behavior Some bands will have multiple stallions The subordinate stallions are more likely to help defend the band than the dominant stallion However these stallions are forced to stay on the periphery of the group by the dominant stallion

Grazing Behavior The time spent grazing is dependent on the intake of the grazer Daily intake is determined by Time spent foraging Varies from a few minutes to 13hrs and 25 min Bite rate Bite size Are selective when quantity and quality of forage is high When drops below a threshold level they become less selective

Grazing Behavior Foraging time increases for mares in the summer months Major feeding bouts after dawn and before dusk Feed mainly during the day except for summer months when there is a midday lull

Grazing Behavior Often forage from plant communities that are continuous with patches of more desirable plants May use spatial memory to find those plants that are the most desirable Study by Edwards et al., 1996

Grazing Behavior Most large herbivores rest in the areas that they graze Some herds have been shown to travel over 1 kilometer to high ground, saltflats with low plant cover, or denuded vegetation Yet when they arrive they show signs of extreme discomfort

Grazing Behavior So why travel all that distance? Higher altitude cooler temps? Unlikely, cooler temps are more likely to be found in shady areas rather than bare ground Fewer biting flies? Probably, though the reasons are unclear Most likely the flat, open areas are poor habitat for biting flies

Grazing Behavior Is it really worth the effort? They can lose up to 500cc of blood to biting flies a day Biting flies are also the carriers of disease Anthrax Lethal arbovirsues Horses actually spend less energy in the comfort movements

Grazing Preferences Preferences Prefer gentler slopes Mesic grasslands Avoid Steep slopes Drier grasslands Large tracks of forests

Home Range Home range varies in size in relation to the band size Home ranges overlap Groups can move seasonally Home range cores become larger during winter months than in summer months Change elevations for foaling and mating

Methods Focal animal Focal groups

Problems In feral herds it is often times difficult to identify individuals Identify distinctive individuals Markings Colorations Sex Location Counting by helicopter

Conclusion Horses are for the most part herd animals and they move as a herd, but can be influenced by individualistic behaviors There are reasons and patterns in their movements that can be predicted when their behavior is understood

Possible Implications Understanding behavior can allow Better prediction of movements Understanding habitat choice Better herd management

Questions Questions?