Marian Stamp Dawkins

Receiver psychology and the evolution of animal signals

Abstract Despite decades of interest, the adaptive significance of the extraordinary diversity in the design of animal signals remains elusive. It is suggested that signal design consists of two components: ‘strategic design’ and ‘efficacy’. Strategic design is concerned with how a signal is constructed by natural selection to provide the information necessary to make a receiver respond (e.g. by being good at displaying underlying quality), whilst efficacy is concerned with how a signal is designed to get that information across to the receiver (e.g. by being easily measured). It is argued that an important but neglected evolutionary force on animal signals is therefore the psychology of the signal receiver, and that three aspects of receiver psychology (what a receiver finds easy to detect, easy to discriminate and easy to remember) constitute powerful selective forces in signal design. Greatest emphasis is given to memorability because this has been least considered by previous authors. It is argued that learning and memory are involved in a wide range of signals, and numerous hypotheses as to how signals may be adapted to be more memorable to receivers are suggested. The relationship of this analysis to earlier attempts at understanding signals is explored, particularly with reference to the concepts of honesty, manipulation and mind-reading.

From an animal's point of view: Motivation, fitness, and animal welfare

To study animal welfare empirically we need an objective basis for deciding when an animal is suffering. Suffering includes a wide range ofunpleasant emotional states such as fear, boredom, pain, and hunger. Suffering has evolved as a mechanism for avoiding sources ofdanger and threats to fitness. Captive animals often suffer in situations in which they are prevented from doing something that they are highly motivated to do. The “price” an animal is prepared to pay to attain or to escape a situation is an index ofhow the animal “feels” about that situation. Withholding conditions or commodities for which an animal shows “inelastic demand” (i.e., for which it continues to work despite increasing costs) is very likely to cause suffering. In designing environments for animals in zoos, farms, and laboratories, priority should be given to features for which animals show inelastic demand. The care ofanimals can thereby be based on an objective, animal-centered assessment of their needs.

Sustainable Intensification in Agriculture: Premises and Policies

Clearer understanding is needed of the premises underlying SI and how it relates to food-system priorities. Food security is high on the global policy agenda. Demand for food is increasing as populations grow and gain wealth to purchase more varied and resource-intensive diets. There is increased competition for land, water, energy, and other inputs into food production. Climate change poses challenges to agriculture, particularly in developing countries (1), and many current farming practices damage the environment and are a major source of greenhouse gases (GHG). In an increasingly globalized world, food insecurity in one region can have widespread political and economic ramifications (2).

Chicken welfare is influenced more by housing conditions than by stocking density

Intensive broiler (meat) chicken production now exceeds 800 million birds each year in the United Kingdom and 2 × 1010 birds worldwide, but it attracts accusations of poor welfare. The European Union is currently adopting standards for broilers aimed at a chief welfare concern—namely, overcrowding—by limiting maximum ‘stocking density’ (bird weight per unit area). It is not clear, however, whether this will genuinely improve bird welfare because evidence is contradictory. Here we report on broiler welfare in relation to the European Union proposals through a large-scale study (2.7 million birds) with the unprecedented cooperation of ten major broiler producers in an experimental manipulation of stocking density under a range of commercial conditions. Producer companies stocked birds to five different final densities, but otherwise followed company practice, which we recorded in addition to temperature, humidity, litter and air quality. We assessed welfare through mortality, physiology, behaviour and health, with an emphasis on leg health and walking ability. Our results show that differences among producers in the environment that they provide for chickens have more impact on welfare than has stocking density itself.

BATTERY HENS NAME THEIR PRICE: CONSUMER DEMAND THEORY AND THE MEASUREMENT OF ETHOLOGICAL 'NEEDS'

Abstract The concept of an ‘ethological need’ has assumed a prominent place in recent discussions of animal welfare, although the term itself is surrounded by confusion. It is here argued that some of this confusion might be overcome by applying consumer demand theory to some of the problems of animal welfare. As an example, the postulated ‘need’ of battery-caged hens to scratch and dustbathe is reinterpreted in this light, using the economic definition of a ‘necessity’. Two attempts to measure the value that hens put on access to litter are reported. In experiment 1, birds were required to make an instantaneous choice between food and litter under different degrees of food deprivation. In experiment 2, choices were observed over longer periods of time under changes of income (time available). In neither case was there evidence of hens regarding litter as a necessity but these results should be regarded only as preliminary.

Behavioural deprivation: A central problem in animal welfare

Abstract A key issue in animal welfare is whether keeping animals in conditions where they cannot or do not perform behaviour typical of more naturally-kept members of their species causes them to suffer. Various measures have been used to resolve this issue. The cost an animal is prepared to pay for the opportunity to perform different behaviour can be used as a measure of the importance of that behaviour to the animal. Manipulation of time-budgets is the most reliable method of measuring such costs and of relating “deprivation” to “suffering”.

Perceptual changes in chicks: Another look at the ‘search image’ concept

Abstract Although at first unable to detect grains of rice dyed the same colour as the background, chicks subsequently showed a striking improvement in their ability to detect this ‘cryptic’ food (experiment 1). This change is most plausibly seen as a central change of perception (experiment 2). Ability to see cryptic rice was not fully retained from one day to the next (experiment 3). Feeding chicks on conspicuous grains had an adverse effect on their ability to detect cryptic grains (experiment 4). These results are compatible with L. Tinbergens hypothesis that birds may use ‘searching images’, but it is argued that this term itself is unhelpful.

The corruption of honest signalling

Abstract It is argued that recent analyses of the evolution of animal signals, which claim that signalling systems must be honest indicators of underlying quality, have neglected a vital consideration: the costs receivers pay in assessment. Where the costs of fully assessing a signaller are high, in terms of energy, time, or risk, and the value of the extra information gained is low, then it will pay receivers to settle for cheaper, but less reliable, indicators of quality instead. Thus, it is argued, honest assessment will be replaced by conventional signalling. Conventional signals are open to cheating, but cheating will be kept at low frequencies by the frequency-dependent benefits of occasional assessment (or ‘probing’), so dishonest signalling remains stable. The concept of ‘honesty’ is discussed.

Time budgets in Red Junglefowl as a baseline for the assessment of welfare in domestic fowl

Abstract A study of the way in which semi-wild junglefowl allocate their time between different activities showed that in 60% of all minutes during the active part of the day, hens were seen to be ground pecking and in 34%, ground scratching. The fact that such a high proportion of time was spent in foraging activities is discussed in relation to the welfare of domestic fowl unable to perform such activities.

DO HENS SUFFER IN BATTERY CAGES? ENVIRONMENTAL PREFERENCES AND WELFARE

Abstract The question ‘Do hens suffer in battery cages?’ is difficult to answer because of the problem of objectively assessing suffering in animals. It is argued that preference tests may be one way of throwing light on this difficult problem. This paper describes some experiments on habitat preference in domestic hens. No preference was observed between a commercial battery cage and a large pen when hens were given continuous access to the two. A simultaneous choice between a battery cage and an outside hen-run showed a clear preference for the run, but choice was strongly influenced by prior experience. The strength of the run preference was investigated by ‘pitting’ the run against food and access to companions.