Mental Experiences in Wild Animals: Scientifically Validating Measurable Welfare Indicators in Free-Roaming Horses

Abstract

The mental experiences of animals are what characterises their welfare status. The Five Domains Model for assessing welfare aligns with the understanding that physical and mental states are linked. Following measurement of indicators within each of the four physical/functional Domains (1. Nutrition; 2. Physical environment; 3. Health; and 4. Behavioural interactions), the anticipated negative or positive affective consequences (mental experiences) are cautiously inferred and assigned to Domain 5. Those inferences derive credibility from validated knowledge of the underlying systems of physiology, neurophysiology, neuroethology and affective neuroscience. Any indicators used for assessing welfare need to be scientifically validated. This requires, firstly, evidence of the links between a measurable/observable indicator and the physical/functional impact (in Domains 1 to 4), and secondly, a demonstrable relationship between the physical/functional impact and the mental experience it is inferred the indicators reflect (in Domain five). This review refers to indicators of physical/functional states in Domains 1 to 4, which have been shown to be measurable in free-roaming wild horses, and then evaluates the scientific evidence linking them to inferred mental experiences in Domain 5. This is the first time that the scientific evidence validating a comprehensive range of welfare indicators has been synthesised in this way. Inserting these indicators into the Five Domains Model enables transparently justifiable assessment and grading of welfare status in free-roaming horses.

Rethinking the utility of the Five Domains model

“…The Five Domains has seen perhaps the widest uptake in the field of wildlife management. It has been adopted for over ten years to assess practices used to kill and remove introduced wildlife species in Australia (Sharp & Saunders 2011;Hampton et al 2016a;Harvey et al 2020Harvey et al , 2021Harvey et al , 2023. It has since been applied to introduced wildlife in New Zealand (Beausoleil et al 2016), nuisance ('pest') native wildlife species in the United Kingdom (Baker et al 2016(Baker et al , 2022 and other countries such as Belgium (De Ruyver et al 2023).…”

“…Seventh, there is a need for better, well-validated, animal-based measures for many species and management contexts (Harvey et al 2023 ).…”

How Useful Are Existing Protocols in the Quick Assessment of the Welfare of Semi-Feral Horses? Pilot Study on Konik Polski Horses Living in the Forest Sanctuary

“…Observations of feral horses living in naturalistic conditions provide knowledge about all aspects of the behaviour of the species [ 12 ], which is often used as a welfare reference for horses living in human-controlled conditions. However, it has been shown that free-living horses can also suffer from decreased welfare [ 13 , 14 ]; here we define animal welfare according to [ 15 ]: ‘welfare corresponds to the absence of negative subjective emotional states, usually called “suffering” and probably with the presence of positive subjective emotional states, usually called “pleasure”’. Poor welfare could occur in free-living horses due to their inability to meet their core nutritional requirements, for example, when horses suffer a shortage of forage due to the season (in winter or due to drought, [ 14 ] or due to overgrazing [ 16 ].…”

“…However, it has been shown that free-living horses can also suffer from decreased welfare [ 13 , 14 ]; here we define animal welfare according to [ 15 ]: ‘welfare corresponds to the absence of negative subjective emotional states, usually called “suffering” and probably with the presence of positive subjective emotional states, usually called “pleasure”’. Poor welfare could occur in free-living horses due to their inability to meet their core nutritional requirements, for example, when horses suffer a shortage of forage due to the season (in winter or due to drought, [ 14 ] or due to overgrazing [ 16 ]. At the opposite end of the spectrum, obesity can be a frequent problem in native horse breeds in the high grazing season; this could be another welfare issue in free-living horses [ 17 , 18 ].…”

“…The quality of water can sometimes be poor as horses trample the borders of natural waterholes making them swampy and dirty. Feral and semi-feral populations living in rocky or swamp environments are also at risk of injuries or fatal incidents due to rough terrain [ 13 , 14 ]. They can also sustain injuries as a consequence of fights between stallions and stallion harassment [ 20 ], infected insect bites [ 21 ], high levels of parasitism [ 22 , 23 , 24 ] or predator attacks [ 25 , 26 ], and hoof and leg deformations causing lameness [ 17 , 18 ].…”