Seals are a widely distributed and diverse semi-aquaticmarine mammal. They spend most of their lives in the water, but come ashore to mate, give birth, molt or escape from predators such as sharks and killer whales. They feed largely on fish and marine invertebrates; but a few, like the leopard seal, feed on large vertebrates, such as penguins and other seals.
When they are on the land, they live in large social colonies which may contain over one thousand seals.
Seals have remarkable physiological adaptations which allow them to survive within their aquatic environment. They can dive to depths of over 1000 feet and some species have been recorded holding their breath for up to two hours. They can do this as they have a higher concentration of haemoglobin in their blood and large amounts of myoglobin in their muscles. Both haemoglobin and myoglobin are oxygen-carrying compounds, therefore, when diving or swimming, they can store oxygen in their blood and muscles and dive for long periods. Like cetaceans, they also conserve oxygen when diving by restricting blood flow to only vital organs and slowing their heart rates by 50-80%. In a study of northern elephant seals, the seal’s heart rate was reduced from 112 beats per minute at rest to 20-50 beats per minute when diving.
It is also now apparent that seals also have extraordinary mental capabilities, and we have recently discovered they can understand the concept of time in the same way in which we do.
Many animals follow daily schedules or seasonal cycles, but little research has been carried out to distinguish their ability to understand time such as the difference between three seconds and thirteen seconds.
Behavioural researchers at the Marine Science Center at the University of Rostock tested this ability with an 11-year-old Harbor seal known as Luca. They displayed a white circle on a black computer screen for a period of three to 30 seconds, paused and then flashed the circle again. The researchers trained Luca to press one button if he thought the second display was longer and another if he thought both displays were of equal length. When he was correct, he enjoyed a tasty herring treat.
The team found that Luca could detect differences as short as 420 milliseconds. In other words, he could distinguish a three-second display from one lasting 3.42 seconds. This research was the first time the ability to measure time has been reported in seals.
The researcher’s hypothesis that seals may have evolved this skill to make split-second decisions while chasing fish or to identify vocalizations made at different rates by other seals.
Seals truly are amazing animals
Seal populations are often severely impacted by ocean pollution and oil spills, seals are also victim of the commercial seal hunt as their furs are still valued within the fashion industry. Large numbers are also killed due to the competition they are perceived to present to commercial fisheries.
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Seals in captivity
Many thousands of seals are held in aquariums, zoos and ocean parks across the world. The conditions for these individuals vary considerably, with many held in very poor and often stressful conditions. Seals are wide-ranging, social animals with diverse physical, social, behavioural and psychological needs. Keeping seals within environments that do not allow them to perform their natural behaviours leads to them suffering unnecessarily.
Individuals in captivity cannot express their natural behavioral repertoire. They cannot engage with their environment or express their preferences. They cannot forage for food, may not be able to create social bonds of their choosing and ultimately cannot control their environment. (1)
The organisation of a seal’s behavior in the wild is primarily regulated by external stimuli (such as the seal’s haul-out site, the dynamic marine environment, location and movement of prey species, navigation cues, social companions, tides, weather and sea conditions, etc). Many of these external stimuli are not present in captivity. Intelligent mammals such as pinnipeds seek novel and varying stimuli through exploration and play, this scope for investigating novel stimuli is limited or non-existent in most captive pinniped facilities. In the long-term captivity impacts animal behavior gradually affecting its active and flexible character(2). Animals that have developed stereotyped behavior may persist in such stereotypies even when transferred to a more enriched environment or exposed to novel objects.
Enrichments have been introduced to many facilities to improve ‘well-being’ by alleviating boredom and stereotypic behaviors. These might include balls or toys in the pools, devices similar to dog toys that release food as they are moved around, and large ice cubes that contain fish pieces inside. One study(3) of a group of seals at Baltimore Aquarium demonstrated that the introduction of various objects stimulated exploration and random swimming and reduced patterned (stereotypic) swimming. Machines that create wave patterns may also add enrichment. Both seals and sea lions can respond well to human interaction and many zoos and aquaria incorporate positive reinforcement training sessions into the daily routine as additional enrichment.
Where pinnipeds are held in captivity, Animals Asia support behavioural research using positive reinforcement training techniques where the research clearly increases our understanding and appreciation of pinniped species, this benefit must be considered in the context of the welfare and well-being of the animals
Social animals, such as most pinniped species, require companions in captivity, and should not be kept solitarily. Companions can provide an endless variety of meaningful stimulation, but this may only occur to the animals’ benefit if other aspects of the environment, such as physical attributes of the pool and feeding schedule, are also appropriately designed to recognize the interdependence of enrichment measures.(4)
- Wiepkema, P. R. 1985. Abnormal behaviors in farm animals: ethological implications. Netherlands Journal of Zoology 35: 279-299.
- Wemelsfelder, F. Animal Boredom - A Model of Chronic Suffering in Captive Animals and Its Consequences For Environmental Enrichment http://www.torontozoo.com/meet_animals/enrichment/animal_boredom.htm
- Hunter S.A., Bay M.S., Martin M.L. and Hatfield J.S. 2002. Behavioral effects of environmental enrichment on harbor seals (Phoca vitulina concolor) and gray seals (Halichoerus grypus). Zoo Biol 21:375–387.
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