Effects of landmark distance and stability on accuracy of reward relocation

This work was supported by the University of St Andrews, the University of Lethbridge and the Natural Sciences and Engineering Council of Canada.Although small-scale navigation is well studied in a wide range of species, much of what is known about landmark use by vertebrates is based on laboratory experiments. To investigate how vertebrates in the wild use landmarks, we trained wild male rufous hummingbirds to feed from a flower that was placed in a constant spatial relationship with two artificial landmarks. In the first experiment, the landmarks and flower were 0.25, 0.5 or 1 m apart and we always moved them 3–4 m after each visit by the bird. In the second experiment, the landmarks and flower were always 0.25 m apart and we moved them either 1 or 0.25 m between trials. In tests, in which we removed the flower, the hummingbirds stopped closer to the predicted flower location when the landmarks had been closer to the flower during training. However, while the distance that the birds stopped from the landmarks and predicted flower location was unaffected by the distance that the landmarks moved between trials, the birds directed their search nearer to the predicted direction of the flower, relative to the landmarks, when the landmarks and flower were more stable in the environment. In the field, then, landmarks alone were sufficient for the birds to determine the distance of a reward but not its direction.PostprintPostprintPeer reviewe

Diel and Monthly Movement Rates by Migratory and Resident Female Pronghorn

Animal movement patterns are variable, with certain species primarily being diurnal and others nocturnal. Pronghorn (Antilocapra americana) are regarded as diurnal animals moving predominately during daylight hours. Anecdotal accounts, however, suggest that pronghorn move during the night but the extent, frequency, and importance of these nocturnal movement behaviors are unknown. To evaluate movements, we combined global positioning system relocation data from collared female pronghorn in the Northern Sagebrush Steppe between 2003 and 2007 with sunrise/sunset data within a geographical information system platform. We assessed whether mean and maximum movement rates were influenced by diel period (dawn, day, dusk, and night), month (January through December), movement strategy (migrant or resident), and year individuals were captured (2003, 2005, or 2006). Diel period and month greatly influenced mean and mean maximum movement rates. Pronghorn were indeed primarily diurnal in activity but significant movement did occur at night. Our results indicate pronghorn primarily move during the daytime, a period when humans also are most active on the landscape. This movement cycle has important implications for management and conservation of pronghorn at the northern periphery of its range

From a sequential pattern, temporal adjustments emerge in hummingbird traplining

Animals that feed from resources that are constant in space and that refill may benefit from repeating the order in which they visit locations. This is a behavior known as traplining, a spatial phenomenon. Hummingbirds, like other central‐place foragers, use short traplines when moving between several rewarding sites. Here we investigated whether traplining hummingbirds also use relevant temporal information when choosing which flowers to visit. Wild rufous hummingbirds that were allowed to visit 3 artificial flower patches in which flowers were refilled 20 min after they had been depleted repeated the order in which they visited the 3 patches. Although they tended to visit the first 2 patches sooner than 20 min, they visited the third patch at approximately 20‐min intervals. The time between visits to the patches increased across the experiment, suggesting that the birds learned to wait longer before visiting a patch. The birds appeared to couple the sequential pattern of a trapline with temporal regularity, to some degree. This suggests that there is a temporal component to the repeated spatial movements flown by foraging wild hummingbirds.PostprintPeer reviewe

Wild rufous hummingbirds use local landmarks to return to rewarded locations

This work was supported by the University of St Andrews, the University of Lethbridge and the Natural Sciences and Engineering Council of Canada.Animals may remember an important location with reference to one or more visual landmarks. In the laboratory, birds and mammals often preferentially use landmarks near a goal (“local landmarks”) to return to that location at a later date. Although we know very little about how animals in the wild use landmarks to remember locations, mammals in the wild appear to prefer to use distant landmarks to return to rewarded locations. To examine what cues wild birds use when returning to a goal, we trained free-living hummingbirds to search for a reward at a location that was specified by three nearby visual landmarks. Following training we expanded the landmark array to test the extent that the birds relied on the local landmarks to return to the reward. During the test the hummingbirds' search was best explained by the birds having used the experimental landmarks to remember the reward location. How the birds used the landmarks was not clear and seemed to change over the course of each test. These wild hummingbirds, then, can learn locations in reference to nearby visual landmarks.PostprintPeer reviewe

Size is relative : use of relational concepts by wild hummingbirds

This work was supported by the Association for the Study of Animal Behaviour (S.D.H.), the University of Lethbridge and the Natural Sciences and Engineering Research Council of Canada (RGPIN 121496–2003; T.A.H.).Rufous hummingbirds (Selasphorus rufus) will readily learn the location and the colour of rewarded flowers within their territory. But if these birds could apply a relational concept such as ‘the larger flowers have more nectar’, they could forego learning the locations of hundreds of individual flowers. Here, we investigated whether wild male territorial rufous hummingbirds might use ‘larger than’ and ‘smaller than’ relational rules and apply them to flowers of different sizes. Subjects were trained to feed consistently from one of two flowers. Although the flowers differed only in size, the reward was always contained in the same-size flower. The birds were then tested on a choice of two empty flowers: one of the familiar size and the other a novel size. Hummingbirds applied relational rules by choosing the flower that was of the correct relational size rather than visiting the flower of the size rewarded during training. The choices made by the hummingbirds were not consistent with alternative mechanisms such as peak shift or associative learning. We suggest that while hummingbirds are very good at remembering the spatial locations of rewarding flowers, they would be able to use relative rules when foraging in new and changing environments.Publisher PDFPeer reviewe

Why study cognition in the wild (and how to test it)?

An animal's behavior is affected by its cognitive abilities, which are, in turn, a consequence of the environment in which an animal has evolved and developed. Although behavioral ecologists have been studying animals in their natural environment for several decades, over much the same period animal cognition has been studied almost exclusively in the laboratory. Traditionally, the study of animal cognition has been based on well-established paradigms used to investigate well-defined cognitive processes. This allows identification of what animals can do, but may not, however, always reflect what animals actually do in the wild. As both ecologists and some psychologists increasingly try to explain behaviors observable only in wild animals, we review the different motivations and methodologies used to study cognition in the wild and identify some of the challenges that accompany the combination of a naturalistic approach together with typical psychological testing paradigms. We think that studying animal cognition in the wild is likely to be most productive when the questions addressed correspond to the species’ ecology and when laboratory cognitive tests are appropriately adapted for use in the field. Furthermore, recent methodological and technological advances will likely allow significant expansion of the species and questions that can be addressed in the wild.PostprintPostprintPeer reviewe

Numerical ordinality in a wild nectarivore

This work was supported by the Association for the Study of Animal Behaviour (S.D.H.), the University of Lethbridge, and the Natural Sciences and Engineering Research Council of Canada (RGPIN 121496-2003; T.A.H.)Ordinality is a numerical property that nectarivores may use to remember the specific order in which to visit a sequence of flowers, a foraging strategy also known as traplining. In this experiment, we tested whether wild, free-living rufous hummingbirds (Selasphorus rufus) could use ordinality to visit a rewarded flower. Birds were presented with a series of linear arrays of 10 artificial flowers; only one flower in each array was rewarded with sucrose solution. During training, birds learned to locate the correct flower independent of absolute spatial location. The birds' accuracy was independent of the rewarded ordinal position (1st, 2nd, 3rd or 4th), which suggests that they used an object-indexing mechanism of numerical processing, rather than a magnitude-based system. When distance cues between flowers were made irrelevant during test trials, birds could still locate the correct flower. The distribution of errors during both training and testing indicates that the birds may have used a so-called working up strategy to locate the correct ordinal position. These results provide the first demonstration of numerical ordinal abilities in a wild vertebrate and suggest that such abilities could be used during foraging in the wild.PostprintPeer reviewe

Estimating on the fly : the approximate number system in rufous hummingbirds (Selasphorus rufus)

Funding: Association for the Study of Animal Behaviour.When presented with resources that differ in quantity, many animals use a numerosity system to discriminate between them. One taxonomically widespread system is the approximate number system. This is a numerosity system that allows the rapid evaluation of the number of objects in a group and which is regulated by Weber’s Law. Here we investigated whether wild, free-living rufous hummingbirds (Selasphorus rufus) possess an approximate number system. The hummingbirds were presented with two experiments. In the first we investigated whether hummingbirds spontaneously chose an array containing more flowers than an alternate array. In the second we asked whether the hummingbirds could learn to use numerosity as a cue to which of two arrays contained the better reward. The birds did not spontaneously prefer an array containing more flowers. After minimal training, however, they learned to choose the more numerous array and could differentiate between arrays of five and seven flowers. These data support the presence of an approximate number system in the rufous hummingbird. It seems plausible that having such a system would enable much more efficient foraging in this species.Publisher PDFPeer reviewe

Assessment of health in human faces is context-dependent

This work was supported by the National Environment Research Council, UK (KM), Unilever Research & Development USA and the Economic and Social Research Council (RW, DP).When making decisions between options, humans are expected to choose the option that returns the highest benefit. In practice, however, adding inferior alternatives to the choice set can alter these decisions. Here we investigated whether decisions over the facial features that people find healthy looking can also be affected by the context in which they see those faces. To do this we examined the effect of choice set on the perception of health of images of faces of light-skinned Caucasian females. We manipulated apparent facial health by changing yellowness of the skin: the healthy faces were moderately yellow and the less healthy faces were either much more yellow or much less yellow. In each experiment, two healthy faces were presented along with a third, less healthy face. When the third face was much more yellow, participants chose the more yellow of the two healthy faces more often as the most healthy. However, when the third face was the least yellow, participants chose the less yellow of the two healthy faces more often. A further experiment confirmed that this result is not due to a generalised preference for an intermediate option. These results extend our understanding of context-dependent decision-making in humans, and suggest that comparative evaluation may be a common feature across many different kinds of choices that humans have to make.PostprintPeer reviewe

Wild hummingbirds require a consistent view of landmarks to pinpoint a goal location

Funding: This work was supported by the University of St Andrews, the University of Lethbridge and the Natural Sciences and Engineering Council of Canada.One outcome of the extensive work on the ways that birds and insects use visual landmarks to return to a rewarded location is that they use landmarks differently. But this conclusion may have been reached because the almost exclusive training and testing of birds in small laboratory environments may prevent birds from using the view-matching strategies seen in insects. To test how birds use landmarks in an open-field environment, we trained free-living hummingbirds to search for a reward near two experimental landmarks. When the angular size and panoramic position of the landmarks were kept consistent, the hummingbirds searched in the direction of the flower and matched either the retinal angle of the landmarks or the absolute distance of the flower during training, even when the actual size and distance between landmarks changed. These data are more similar to data from view-matching ants solving a similar problem than they are to data from birds trained to use landmarks in the laboratory. This suggests that hummingbirds may also use a remembered view to relocate a rewarded site. Regardless of whether hummingbirds use a remembered view for navigation or just to recognize landmarks, data on landmark use collected from birds tested in the laboratory may not fully reflect how birds return to locations in the wild.PostprintPeer reviewe