Giving animals their preferred items (e.g., environmental enrichment) has been suggested as a method to improve animal welfare, thus raising the question of how to determine what animals want. Most studies have employed choice tests for detecting animal preferences. However, whether choice tests represent animal preferences remains a matter of controversy. Here, we present a history-based method to analyse data from individual choice tests to discriminate between preferred and non-preferred items. This method differentially weighs choices from older and recent tests performed over time. Accordingly, we provide both a preference index that identifies preferred items contrasted with non-preferred items in successive multiple-choice tests and methods to detect the strength of animal preferences for each item. We achieved this goal by investigating colour choices in the Nile tilapia fish species.

Environmental enrichment (EE) can improve the welfare of captive fish. Its objective is to provide new sensorial and motor stimulation in order to help meet their behavioural, physiological, morphological and psychological needs, whilst reducing stress and frequency of abnormal behaviours. In fish farms, rearing environments are usually designed from a human perspective and based on economic requirements, mainly for practical reasons for the farmer, with little consideration for animal welfare. Throughout aquaculture production cycles, many farming operations can be stressful for fish, and EE may not only help them cope with these stressful events but also improve their overall welfare. In recent years, increasing interest on the effects of EE in captive fish has focussed mainly on structural enrichment. However, there are many other enrichment strategies that merit attention (e.g. sensorial, occupational, social and dietary enrichment) and which may be of interest for fish farming. Here, we review in depth the existing literature on EE and its effects on the welfare of a wide range of farmed fish species, discussing the feasibility and potential applications of different EE strategies to promote fish welfare at a commercial scale. We also present a practical framework to address the design, validation and implementation of EE by the aquaculture industry, taking in consideration the technical challenges of providing enrichment for farmed fish.

Animal preference and motivation have been used to assess different kinds of environmental resources that may help improve welfare conditions. However, preference and motivation are typically tested separately, and these assays disregard the individual nature of responses. Here, in rainbow trout (Oncorhynchus mykiss), we evaluated individual variability of preference for different resources, and whether these fish are motivated to access such preferred options. Individual fish were allowed to sample among four different compartments. Two different tests were used, one where the compartments varied in background colour, the other where the compartments varied in what they contained. Over a series of 10 days, the fish interacted with these different options and during the trials of the last 7 days, their visitation frequency to each compartment was registered every 30 s. The data were used to calculate a preference index for each fish. Physical motivation of individual fish to access preferred and dispreferred options was then tested by quantifying the frequency of pushes the fish gave to transparent hinged doors that led to the different compartments. In a separate test, whether fish entered a preferred or a dispreferred option after crossing an aversive open and brightly lit, along area was used as a measure of psychological motivation. Trout showed a strong preference for blue backgrounds, and were both more physically and psychologically motivated to access this color. However, preference and motivation for alternative items such as shelters or conspecifics were more variable. We conclude that the physical and psychological motivation of trout depend on the resources that they are trying to access, but the fish express stronger motivation to gain access to more preferred options.

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The identification of animal preferences is assumed to provide better rearing environments for the animals in question. Preference tests focus on the frequency of approaches or the time an animal spends in proximity to each item of the investigated resource during a multiple-choice trial. Recently, a preference index (PI) was proposed to differentiate animal preferences from momentary responses (Sci Rep, 2016, 6:28328, DOI: 10.1038/srep28328). This index also quantifies the degree of preference for each item. Each choice response is also weighted, with the most recent responses weighted more heavily, but the index includes the entire bank of tests, and thus represents a history-based approach. In this study, we compared this PI to motivation tests, which consider how much effort is expended to access a resource. We performed choice tests over 7 consecutive days for 34 Nile tilapia fish that presented with different colored compartments in each test. We first detected the preferred and non-preferred colors of each fish using the PI and then tested their motivation to reach these compartments. We found that fish preferences varied individually, but the results were consistent with the motivation profiles, as individual fish were more motivated (the number of touches made on transparent, hinged doors that prevented access to the resource) to access their preferred items. On average, most of the 34 fish avoided the color yellow and showed less motivation to reach yellow and red colors. The fish also exhibited greater motivation to access blue and green colors (the most preferred colors). These results corroborate the PI as a reliable tool for the identification of animal preferences. We recommend this index to animal keepers and researchers to identify an animal’s preferred conditions.

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This study analyzed the effects of noise levels and number of visitors on the behaviors of a mother puma and her daughter in a zoo environment with respect to the time of day. The study monitored visitation (noise and number) over two 1-week periods (4 weeks between periods) and frequency of various puma behaviors (videorecorded). The study analyzed videotaped behavior of the pumas based on the time of day and visitors' number and noise levels. There was a direct association of puma behaviors with visitors' number and noise levels. The daughter puma was the most affected and behavioral changes of both pumas correlated more strongly with the noise level than the number of visitors. The noise level and number of visitors affected the behavior of the mother and her daughter only in the morning. The results of this study indicate that both noise level and number of visitors affected these pumas but revealed the noise as predominant. Moreover, the response of these pumas to visitors depended on the time of the day.

Abstract:The effects of different environmental enrichments on the behaviors of four captive jaguars, Panthera onca (Carnivora, Felidae), were individually evaluated. The frequency of jaguar behaviors were recorded in three phases: before, during and after environmental enrichments application. These included hose ball, scent trail, meat tubes, cardboard boxes with meat or elephant feces, stuffed pumpkins, meat ice cream, meat with animal hair, bags with meat, and sounds. The enrichments reduced inactivity and the time duration when jaguars were out of sight, and increased general activity and maintenance behaviors of all tested jaguars. However, the behavioral responses expressed considering other behaviors and after the removal of environmental enrichments varied among individuals. When there were no more enrichments in their enclosures, two jaguars seemed to be in a worse condition than before the introduction of them, while the oldest jaguar maintained all the positive effects. The other jaguar expressed intermediate responses between these two patterns after the removal of the enrichments. Although the tested enrichments improved the welfare of the jaguars, we conclude that individual variability of response to the enrichments highlights the need to consider individual variation in future studies, since some individuals may take better advantages from the enrichments than others.