Food Imprinting Research Articles

Innate response to first feeding in Octopus berrima hatchlings despite embryonic food imprinting

Abstract Food imprinting has both ecological and evolutionary significance but the generality of these patterns for octopods remains unknown. We aim to determine the prey preference of Octopus berrima hatchlings and whether it may be modified through imprinting. Firstly, hatchlings were given isopods, amphipods and mussels to determine their prey preference ranking. In a separate experiment, embryos were exposed to the visual and chemical stimuli of either isopods, amphipods or mussels separately at least a week before hatching. A prey preference test on hatchlings using all three prey types was conducted. We found that O. berrima had a preference ranking of isopods > amphipods > mussels. However, they retained their isopod prey preference regardless of the prey type they were embryonically exposed to, indicating that it is likely pre-determined as a result of innate biological processes rather than from life experience, providing evidence that imprinting does not occur in O. berrima.

Food imprinting and visual generalization in embryos and newly hatched cuttlefish, Sepia officinalis

Juvenile cuttlefish spontaneously prefer shrimp to crabs. This preference can be changed by early visual learning during embryonic and postembryonic life and has been related to a form of food imprinting. Nevertheless, it is unknown whether generalization occurs in conjunction with this early learning process. We found that inexperienced hatchling cuttlefish preferred ‘black’ to ‘white crab’ for their first meal, the black ink envelope of cuttlefish eggs did not prevent embryos discriminating between black and white crabs and embryonic or postembryonic visual familiarization to ‘white crabs’ induced a subsequent visual preference for ‘white crabs’ over ‘black crabs’ in the hatchling's first meal. Finally, juvenile cuttlefish previously pre- or postnatally exposed to ‘white crabs’ preferred ‘black crabs’ to shrimp, indicating for the first time that prey generalization occurs as early as the embryonic stages in cuttlefish. Such cognitive abilities could confer important adaptive advantages in processing information about prey likely to be available in the egg-laying environment at hatching and in the course of juvenile dispersal.

The influence of dietary arachidonic acid on the immune response and performance of Pacific whiteleg shrimp, Litopenaeus vannamei, at high stocking density

Stocking shrimp at high densities increases yield during culture, but growth is generally compromised and weakened immune response associated with poor water quality has also been reported. Therefore, we tested if supplying more arachidonic acid (ARA) in the diet, a precursor of eicosanoids such as prostaglandins E from the series II (PGE2) that enhance immune response can counteract the negative effect of stocking shrimp at high densities. The effect of physical crowding was separated from the effect of water quality, both a result of high density, by using tanks divided by a hard plastic net that allowed water flow between two density conditions. Crowding reduced weight gain by 8.3%, although the effect was more evident with deteriorated water quality from combined effects of high total ammonia and low dissolved oxygen levels (18.4%), but no effect on survival was found. A clear food imprinting of ARA levels in hemocytes was observed, but ARA did not clearly counteract the negative effects of high density on overall performance. However, ARA could minimize stress response of sampling and enhance some effectors of the immune system, such as clotting and respiratory burst. The increase in PGE2 metabolite in shrimp fed with the high-ARA diet was not consistent, and thus, the effects of ARA were not necessarily mediated by these eicosanoids.

Food imprinting revisited: early learning in foraging predatory mites

Learning is a ubiquitous phenomenon in foraging animals, allowing behavioural optimisation in variable environments. Food imprinting is a specific form of learning restricted to the early stages of life and with long lasting consequences. However, since coining of the term four decades ago, the uniqueness of food imprinting has been largely questioned due to a putative mechanistic similarity with associative learning. Here, we demonstrate food imprinting in the predatory mite Neoseiulus californicus , which primarily feeds on spider mites but may use thrips as alternative prey. Brief (24 h) exposure to thrips (contact without feeding) early in life resulted in shorter attack latencies and consistently higher predation rates on thrips during adulthood. Predation and oviposition rates were positively correlated but oviposition did not differ between naive and experienced females. Our results suggest that food imprinting is indeed special because, unlike associative learning, it occurred without reinforcement, was restricted to a sensitive phase and persisted into adulthood. Food imprinting seems particularly advantageous when prey species availability varies little within generations and a given prey is difficult to ingest for young small but not older larger life stages. Food imprintability could be used to improve the efficacy of biocontrol agents such as N. californicus .

Food imprinting, new evidence from the cuttlefish Sepia officinalis.

Imprinting provides precocial offspring with an efficient means to optimize their subsequent behaviours. We discovered food imprinting using a sophisticated invertebrate model: the cuttlefish. We showed that early juveniles preferred the prey to which they have been visually familiarized, when the amount of information was sufficient and only if such familiarization occurred during a short sensitive period. We also demonstrated that the effects of visual food imprinting overcame those of the first food ingested. Our study shows that visual imprinting is a critical process in animals, surpassing more direct reward experiences that occur outside the critical exposure period.

Temporal and developmental aspects of diet‐induced food preferences in larvae of the tobacco hornworm, Manduca sexta

AbstractDiet‐induced changes in food preferences in an oligophagous caterpillar were studied in order to characterize the conditions under which this induction occurs. The time course of acquisition and extinction of induced food preferences by larvae of the tobacco hornworm, Manduca sexta (Johan.) (Lepidoptera, Sphingidae), was examined by varying the food and duration of larval food experience. Larvae were given feeding experience with the host plant tomato, Lycopersicon esculentum (Mill.) (Solanaceae), or the acceptable non‐host plant cowpea, Vigna unguiculata (Walp.) (Fabaceae), or switched from one to the other during different instars. Food preferences for V. unguiculata by the fourth or fifth instar larvae were measured individually in two‐choice tests with discs of V. unguiculata and moist filter paper. The acquisition or extinction of an induced food preference for V. unguiculata was indicated by larvae preferring V. unguiculata to filter paper or the reverse, respectively. Results showed that: (1) the period required for the acquisition of induced preference for V. unguiculata can be short (36 h), (2) food experience in either the third or fourth instar period is sufficient, and (3) the most recent feeding experience appears to be important. In contrast, the period required for extinction of induced preference for V. unguiculata appeared to be longer (1–3 instars), and both the most recent feeding experience and total duration of larval experience with the inducing food seem to play a role. Experience is not restricted to a particular instar period to acquire or extinguish such an induced food preference. The induced food preference for V. unguiculata was not very rigid and could be reversed by having one instar of feeding experience on L. esculentum. The findings indicate that diet‐induced food preferences in M. sexta contains elements of habituation and associative learning, but do not support food imprinting and induction of oligophagy.

Effects on behaviour and plumage of a key-stimuli floor and a perch in triple cages for laying hens

Three environmental factors were introduced in various combinations with the aim of reducing feather pecking and improving the plumage and welfare in low-density triple cages for light-hybrid laying hens (704 cm 2 per hen): (i) a floor with key stimuli for ground pecking, consisting of blue elliptic spots marked on a white matrix; (ii) a blue-dyed feed given during the sensitive period of food imprinting (0–6 days postnatally); (iii) a round wooden perch (d = 33 mm). The effects on the time budget of behaviour, plumage and production were studied. The key-stimuli floor attracted more attention and pecking than the normal cage floor. Hens in perch cages showed less locomotor activity and pacing than other hens. The utilization of the perch during the daytime was 25.2%, but 40% of the preening and 49% of the sitting was carried out on the perch. The plumage at 50 weeks of age was better in hens which were given both blue feed after hatching and a key-stimuli floor in laying cages, and better in perch cages, than in controls. Hens in perch cages consumed 4% less feed than other hens. The results indicate that it may be possible to counteract the redirection of pecking from ground to feathers by ethological methods which stimulate ground pecking.

Development of Dietary Choice in Livestock on Rangelands and its Implications for Management

Plant species that constitute forage for a given species of livestock vary tremendously throughout the diverse environments inhabited by domestic livestock. Within neurological, morphological and physiological constraints, learning early in life enables herbivores to develop preferences for or aversions to available plants and to acquire the motor skills necessary to harvest and ingest those forages efficiently. Hence, the foraging experiences of young herbivores undoubtedly affect their dietary habits as adults. Three mechanisms help young herbivores to learn efficiently to select appropriate foods: 1) food imprinting, 2) social models and 3) trial and error. Dietary habits of adults apparently are more stable than those of young herbivores. Adults accept new foods less readily, avoid foods that cause gastrointestinal distress to a greater degree, and are influenced less in choice of diet by social models than young animals are. The ability of livestock to learn dietary habits early in life presents both problems and opportunities for managers. Livestock that forage efficiently in the environment where they are reared may not forage as efficiently in a new environment. Diet training may enable managers to create a foraging group more suited to management goals. Additional research is needed to determine how age at which exposure occurs, as well as how duration, intensity, variability and complexity of exposure early in life affect dietary habits of adults. These v~riables affect the efficiency of learning and the persistence of dietary habits and thus are crucial to the development of cost-effective management based on diet training.

Is there a neural basis for olfactory food imprinting in ferrets?

Is there a neural basis for olfactory food imprinting in ferrets?

Influence of early nutritional experience on adult diet choice in the lesser bandicoot rat, Bandicota bengalensis

Evidence for food imprinting in Norway rats is conflicting. Postweaned litters of the lesser bandicoot rat, Bandicota bengalensis , were condition-fed on different foods for fixed periods. Later, as adults, they were tested for food imprinting. Rats exposed to rice, ragi, and standard feed during their infancy preferred these foods to others. A preference for rice developed early in life did not wane. The duration of infant exposure did not affect the formation and retention of preferences. It is suggested that food imprinting may occur after weaning.

Modification of chicks’ pecking preferences: Food imprinting or instrumental conditioning?

Using Hess’ technique, 35 small groups of chicks of age 2–3 days or beyond were reinforced in training with food for pecking at one visual stimulus (S+) and nonreinforced for pecking at another (S−) and subsequently tested in extinction. In training, pecking was strongly conditioned to S+, but in testing, both number of pecks to and preference for S+ declined as in instrumental conditioning, contrary to Hess’ original report. Results are discussed relative to studies exposing chicks to actual food objects, where an imprinting-like phenomenon has been found.

Food imprinting in domestic chicks as a function of social contact and number of companions

Three-day-old cockerel chicks were trained to peck a green stimulus for food in preference to a blue stimulus within a social, visual, or isolated condition (Experiment 1), or within a 1, 2, 3, or 4–5 group (Experiment 2). The chicks were tested on four subsequent nonreinforced days to ascertain the generality of “food imprinting.” On the initial reinforced day, the chicks discriminated between the two stimuli. The social group pecked more than the visual group and the visual more than the isolated, and the larger the group number, the higher the mean rate. Over the nonreinforced days, all groups showed a rapid decline in the frequency of responses. The data were interpreted as extinction rather than as “food imprinting.”

Food imprinting in the domestic chick: A reconsideration

Experimental chicks were trained to peck a green stimulus for food in preference to a blue stimulus at the ages of 1, 3, or 5 days old within a socialized or isolated condition. The birds were tested on four subsequent days without food in order to ascertain the generality of “food imprinting. ” On the initial reinforced day, the chicks discriminated between the two stimuli, older birds pecked more than younger ones, and those within the socialized condition more than the isolated ones. A rapid decline in the frequency of responses over the nonreinforced days was interpreted as extinction of a discriminative response rather than as “food imprinting.”

Innate visual form preferences in the pecking behavior of young chicks.

Abstract1. Young chicks from the age of 1 to 91/2 days were tested daily for unrewarded two-dimensional form preferences in pecking behavior. 2. Forms having a 049 square inch area were found to be preferred, from high to low, as follows: serrated circle, oval, circle, hexagon, star, pentagon, square, rectangle, and diamond. 3. Chicks that were shown the same forms in a smaller size, .012 square inches in area, preferred them in the same order except that star shifted to last place. The smaller forms elicited a higher level of pecking behavior than did the large ones. 4. There were found increases in pecking behavior as a function of age up to the age of 5 days, after which there was a plateau. Up to (but not including) and after the age of 6-61/2 days the order of preferences for the forms was the same. 5. The disruption of the preference hierarchy at the age of 6-61/2 days is discussed in relation to the food imprinting that HESS (1962, 1964) has demonstrated to occur in chicks.

Food imprinting in the snapping turtle, Chelydra serpentina.

Three groups of hatchling snapping turtles, totaling 20, were fed either meat, fish, or worms. When they were tested for preference after 12 daily feedings, each preferred the diet to which it was accustomed. After 12 more days of eating a different food, each still preferred its original diet. A form of imprinting may be operative in the feeding behavior of this species.