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* This is part 1 of the FAQ for alt.animals dolphins.
* This document is maintained by Jaap van der Toorn
* ([email protected]). The intention is to post the latest
* version of the FAQ on the newsgroup once a month.
*
* Please direct any remarks, suggestions, corrections and
* additions to the above e-mail address.
*
* Last update: March 14, 2002
*

1.0 - What is alt.animals.dolphins?

 alt.animals.dolphins is an unmoderated newsgroup for anyone
 interested in dolphins. Unmoderated means that no-one is
 screening the messages before they are put on the newsgroup.
 As a result, you may occassionally see messages on that have
 nothing to do with dolphins. Usually these are advertisements
 for (often dubious) services and get-rich-fast schemes.
 The best way to deal with those is just to ignore them. Do
 not post follow-up messages and do not mail to the sender.
 This will only encourage them to post more messages in the
 future.

 Topics that are suitable for this newsgroups include (but
 are not restricted to): requests for information, exchanges
 of experiences and ideas, news items etc. as long as they
 relate to dolphins and/or whales.

 Do not post pictures in this newsgroup. These are usually
 large and this is not very polite to readers of the group
 that have to pay connection time fees. If you want to make
 pictures available through Usenet, post them in the designated
 newsgroup: alt.binaries.pictures.animals. You can then post
 a short announcement in this group that you have made them
 available there.

 This group is not intended for lengthy discussion on
 political issues, even though these may deal with dolphins.
 A better platform for these discussions is the newsgroup
 talk.politics.animals.

 For issues dealing with large whales, there is a separate
 newsgroup: alt.animals.whales. Not every provider forwards
 its messages, however.

2.0 - GENERAL BIOLOGY

2.1 - How do dolphins sleep?

 Dolphins have to be conscious to breath (Williams et al, 1990).
 This means that they cannot go into a full deep sleep, because
 then they would suffocate.
 Dolphins have "solved" that by letting one half of their brain
 sleep at a time. This has been determined by doing EEG studies
 on dolphins. Dolphins sleep about 8 hours a day in this fashion.
 Recent research confirmed that dolphins have only one eye
 closed when sleeping. The state (open or closed) of one eye
 remains constant for on average an hour, after which it
 switches state (Goley, 1999).
 REM (Rapid Eye Movement) sleep, usually associated with
 dreaming has been recorded only very rarely. Some scientists
 claim dolphins do not have REM sleep at all.

 A dolphin's behavior when sleeping/resting depends on the
 circumstances and possibly on individual preferences. They
 can either:
 - swim slowly and surface every now and then for a breath
 - rest at the surface with their blowhole exposed
 - rest on the bottom (in shallow water) and rise to the surface
   every now and then to breath.


 sources:
 P.D. Goley (1999)
   Behavioral aspects of sleep in Pacific whitesided dolphins
   (Lagenorhynchus obliquidens, Gill 1865)
   Marine Mammal Science 15(4): 1054-1064

 S.H Ridgway (1990)
   The Central Nervous System of the Bottlenose Dolphin,
   in S. Leatherwood and R.R. Reeves: The Bottlenose Dolphin,
   pp. 69-97, Academic Press

 Th.D. Williams, A.L. Williams & M. Stoskopf (1990)
   Marine Mammal Anesthesia. In: L.A. Dierauf (ed.): Handbook
   of Marine Mammal Medicine: Health, Disease and Rehabilitation,
   pp. 175-191 CRC Press, Boca Raton


2.2 - How intelligent are dolphins?

 The short answer to this is that we do not know. There is no
 reliable method to measure intelligence in humans across
 cultures, so it is not surprising that comparing humans,
 dolphins, apes, dogs, etc. is impossible. There are some
 indications of their potential: they are fast learners and
 can generalize (which is also true of pigs, apes). Also they
 can learn to understand complicated language-like commands
 (which is also true of the great apes).

 Suggested reading:
 R.P. Balda, I.M. Pepperberg & A.C. Kamil (eds.) (1998)
    Animal cognition in nature - The convergence of psychology
    and biology in laboratory and field.
    Academic Press, San Diego, London
 R.J. Schusterman, J.A. Thomas & F.G. Wood (eds.) (1986)
    Dolphin cognition and behavior: a comparative approach,
    Lawrence Erlbaum Associates, New Jersey

2.3 - How does the dolphin brain compare to the human brain?

 Whales and dolphins have quite large brains. Most authors
 agree that the size should be viewed in relation to the body
 size. In some comparisons, brain weight to body weight ratio
 is used, but it is now more common to use the so-called
 Encephalization Quotient (EQ), which is calculated as:
   EQ = brain weight / (0.12 * (body weight ^ (2/3)))
 (brain weight, divided by 0.12 time the body weight to the
 power (2/3)). In this formula, brain and body weight should be
 expressed in grammes. In bottlenose dolphins, the EQ lies
 between 4 and 5, in the killer whale between 2.5 and 3, in
 humans in the 6.5-7.5 range.

 However, the structure of the dolphin brain is quite different
 from most land mammals and shows a lot of similarities with
 so-called archetypal mammals like hedgehogs and bats (mammals in
 which the brain structure has changed little since the middle of
 the Tertiary period).

 Dolphin and whale ancestors returned to the sea 50-70 million years
 ago. (Bats have presumably developed their aerial lifestyle in the
 same period). In their adaptation to the aquatic environment, they
 seem to have retained characteristic features of the brain of the
 primitive mammalian species of the time. In cetaceans, the neocortex
 has expanded greatly, but without the substantial reorganization
 in 6 layers seen in most land mammals. The main features in the
 cetacean brain which differ from land mammals are:
 - a thin neocortex (about 1.5 mm, compared to 2.9 mm in humans)
 - rather uniform structure of the cortex
 - low degree of differentiation between cortical layers and cells
 - massive development of the (phylogenetically older) layers I and VI
 - poor development of layers II, III and IV (which are well developed
 in land mammals)
 - the neurons have relatively few primary dendrites and these are
 weakly branched.

 References and suggested reading:
 A. Berta & J.L. Sumich (1999)
    Marine mammals - Evolutionary biology
    Academic Press, San Diego, London
    (ch. 7.3 focuses on senses and the nervous system)
 I.I. Glezer, P.R. Hof, C. Leranth & P.J. Morgane (1992)
    Morphological and histochemical features of odontocete visual
    neocortex: immunocytochemical analysis of pyramidal and
    non-pyramidal populations of neurons.
    in: J.A. Thomas, R.A. Kastelein & A.Y. Supin (eds.):
    Marine Mammal Sensory Systems, pp. 1-38
    Plenum Press, New York, London
 L. Marino (1997)
    The relationship between gestation length, encephalization,
    and body weight in odontocetes.
    Marine Mammal Science 13(1):133-138
 P.J. Morgane, M.S. Jacobs & A. Galaburda (1986a)
    Evolutionary morphology of the dolphin brain
    in: R.J. Schusterman, J.A. Thomas & F.G. Wood (eds.):
    Dolphin cognition and behavior: a comparative approach,
    pp. 5-29
    Lawrence Erlbaum Associates, New Jersey
 P.J. Morgane, M.S. Jacobs & A. Galaburda (1986b)
    Evolutionary aspects of cortical organization in the
    dolphin brain.
    in: M.M. Bryden & R. Harrison (eds.):
    Research on Dolphins, pp. 71-98
    Oxford Science Publications, Clarendon Press, London
 P.J. Morgane & I.I. Glezer (1990)
    Sensory neocortex in dolphin brain
    in: J.A. Thomas & R.A. Kastelein (eds.):
    Sensort Abilities of Cetaceas - Laboratory and Field Evidence,
    pp, 107-136. NATO ASI Series, Series A: Life Sciences vol. 196
    Plenum Press, New York, London
 S.H. Ridgway (1986a)
    Physological observations on dolphin brains
    in: R.J. Schusterman, J.A. Thomas & F.G. Wood (eds.):
    Dolphin cognition and behavior: a comparative approach,
    pp. 31-59
    Lawrence Erlbaum Associates, New Jersey
 S.H. Ridgway (1986b)
    Dolphin brain size
    in: M.M. Bryden & R. Harrison (eds.):
    Research on Dolphins, pp. 59-70
    Oxford Science Publications, Clarendon Press, London

2.4 - How do dolphins communicate and do they have their own
     language?

 Dolphins communicate mainly by means of sounds. These
 sounds include whistles, but also so-called pulsed sounds,
 which are often described as squawks, barks, rasps, etc.
 But they also use breaching (jumping and falling back into
 the water with a loud splash) and pectoral fin (or flipper)
 and tail (or fluke) slaps (hitting the flipper or fluke on
 the water surface). Body posturing and jaw popping also have
 a role in communication. This list is not exhaustive.

 As for language, we do not know if they have one. Several
 studies have demonstrated that dolphins can understand a
 structured language like ours. This same has been demonstrated
 for a number of other animals species as well (gorilla, bonobo,
 California sea lion, parrot). Some studies also indicate that
 dolphin vocalizations are complex enough to support some form
 of language. However, to date it has not been demonstrated yet
 that they indeed use a language for communication among
 themselves.

 Suggested reading:
 R.P. Balda, I.M. Pepperberg & A.C. Kamil (eds.) (1998)
    Animal cognition in nature - The convergence of psychology
    and biology in laboratory and field.
    Academic Press, San Diego, London
 R.J. Schusterman, J.A. Thomas & F.G. Wood (eds.) (1986)
    Dolphin cognition and behavior: a comparative approach,
    Lawrence Erlbaum Associates, New Jersey

2.5 - How does dolphin sonar work?

 Dolphins (and other toothed whales) can produce high pitched
 clicks. When these clicks hit an object, some of the sound
 will echo back to the "sender". By listening to the echo and
 interpreting the time it took before the echo came back, the
 dolphin estimate the distance of the object. (That's why sonar
 is also called echolocation: with information from the echoes,
 a dolphin can locate an object). Depending on the material the
 object is made of, part of the sound may penetrate into the
 object and reflect off internal structure. If the object is a
 fish, some sound will reflect off the skin on the dolphin's
 side, some of the bones, the internal organs and the skin on
 the other side. So one click can result in a number of (weaker)
 echoes. This will give the dolphin some information about the
 structure and size of the fish. By moving its head (thereby
 aiming the clicks at other parts of the fish) the dolphin
 can get more information on other parts of the fish.

 It is like a medical ultrasound probe, but the results are far
 less clear. A medical probe moves back and forth very rapidly,
 much faster than a dolphin can move its head. Also the
 frequency of the sounds of the medical probe is much higher
 than a dolphin's sonar. Therefore the level of detail
 the echoes can provide is much higher in the medical probe.

 For technical information on dolphin sonar, check out the
 following book:
 W.W.L.Au (1993)
   The sonar of dolphins.
   Springer-Verlag New York

2.6 - Can dolphins combine information from their sonar with
     their vision?

 The short answer is: yes, they can. Just like people can
 visualize an object by just touching it, dolphins can get an
 idea of what an object looks like by scanning it with their
 sonar. They can also identify objects with their sonar that
 they have only been able to see. If they form a visual picture
 from the sonar information (visualization) or form an
 acoustical picture from visual information is still unresolved.
 This capability is called cross-modal transfer and it has been
 demonstrated in only a few animal species so far: the
 bottlenose dolphin and the California sea lion.
 See the following references for more details on this subject.

 R.J. Schusterman, D. Kastak & C. Reichmuth (1995)
 Equivalence class formation and cross-modal transfer:
 testing marine mammals.
 In: R.A. Kastelein, J.A. Thomas & P.E. Nachtigall (eds):
 Sensory systems of Aquatic Mammals, pp. 579-584
 De Spil Publishers, Woerden, the Netherlands
 ISBN 90-72743-05-9

 A.A. Pack & L.M. Herman (1995)
 Sensory integration in the bottlenosed dolphin: Immediate
 recognition of complex shapes across the senses of
 echolocation and vision
 J. Acoustical Society of America 98(2) Part 1: 722-733

2.7  - Can dolphins see colors?

 To able to see colors, the retina must have at least 2
 different kinds of cones, with different sensitivities.
 Most mammals have 2 types of cones: L-cones (sensitive to
 long-wavelength light, red to green) and S-cones (sentitive
 to short-wavelength light, blue to violet or near UV). Humans
 and some other primates have 3 types of cones, giving them a
 better color vision. Only a few landmammals have only one
 type of cone, which means they are colorblind. All these
 landmammals are essentially nocturnal animals.

 Whales and dolphins (as well as seals and sea lions) have
 only one type of cone: the L-cones. Although these cones are
 more sensitive for short-wavelength light than the L-cones
 of terrestrial mammals, they still have a very low sensitivity
 for blue light. And because there is only one type of cone,
 they are essentially colorblind (although in theory it is
 possible that there is a very limited form of colorvision
 in some light conditions, when both the rods and the cones
 are active).

 Reference:
 L. Peichl, G. Behrmann & R.H.H. Kr�ger (2001)
 For whales and seals the ocean is not blue: a visual pigment
 loss in marine mammals
 European Journal of Neuroscience, vol. 13: 1520-1528


2.8 - What and how much do dolphins eat?

 Bottlenose dolphins eat several kinds of fish (including
 mullet, mackerel, herring, cod) and squid. The compostion of
 the diet depends very much on what is available in the area
 they live in and also on the season.
 The amount of fish they eat depends on the fish species they
 are feeding on: mackerel and herring have a very high fat
 content and consequently have a high caloric value, whereas
 squid has a very low caloric value, so to get the same energy
 intake (calories) they will need to eat much more if they feed
 on squid than if they feed on mackerel or herring.
 On average an adult dolphin will eat 4-9% of its body weight
 in fish, so a 250 kg (550 lb) dolphin will eat 10-22.5 kg
 (22-50 lb) fish per day.


2.9 - How old can they get?

 The maximum age for bottlenose dolphins is between 40 and 50
 years. The average age a dolphin can get (the life expectancy)
 can be calculated from the Annual Survival Rate (the percentage
 of animals alive at a certain point, that is still alive one
 year later). For the dolphin population in Sarasota Bay, the
 ASR has been measured to be about 0.961. This yields a life
 expectancy of about 25 years. For the population in the
 Indian/Banana River area, the ASR is between 0.908 and 0.931.
 This yields a life expectance between 10.3 and 14 years.
 So the actual life expectancy differs per region.

 sources:
 R.S. Wells & M.D. Scott (1990)
   Estimating bottlenose dolphin population parameters from
   individual identification and capture-release techniques.
   Report International Whaling Commission (Special Issue 12):
   407-415

 S.L.Hersch, D.K.Odell & E.D.Asper (1990)
   Bottlenose dolphin mortality patterns in the Indian/Banana
   River System of Florida, in S. Leatherwood and R.R. Reeves:
   The Bottlenose Dolphin, pp. 155-164, Academic Press


2.10 - Do dolphins live shorter in captivity?

 There is no evidence to support that statement.
 A recent study, comparing the survival of dolphins in
 captivity from 1940 through 1992 showed no significant
 difference in ASR between the "captive population" and the
 Sarasota Bay population. The ASR for the captive population
 was 0.944 (life expectancy: 17.4 years).
 Also in captivity dolphins have reached ages over 40 years.

 source:
 R.J.Small & D.P.DeMaster (1995)
   Survival of five species of captive marine mammals.
   Marine Mammal Science 11(2):209-226.


2.11 - How did dolphins evolve?

 The earliest recognizable cetaceans lived about 50 million
 years ago. These evolved from the Mesonychids: large land
 mammals, some of which were carnivorous, some herbivorous.
 The earliest cetaceans were members of the now extinct family
 Archaeoceti (the best known of which are Zeuglodon and
 Basilosaurus). 38-25 million years ago the Archaeoceti
 disappeared and were replaced by the early Odontocetes (toothed
 whales) and Mysticetes (baleen whales). The earliest dolphins
 appeared in the late Miocene period, some 11 million years ago.

 The land animals that are closest to whales and dolphins are
 the Ungulates (hoofed animals). This was determined among
 others by comparing the structure of body proteins. The closest
 relative is probably the hippopotamus (Ursing and Arnason, 1998).

 sources:
 P.G.H.Evans (1987)
   The Natural History of Whales and Dolphins.
   Christoper Helm Publishers, London.
 B.M. Ursing & U. Arnason (1998)
   Analyses of mitochondrial genomes strongly support
   a hippopotamus-whale clade
   Proceedings of the Royal Society of London B 265: 2251-2255


2.12 - How can you interact with wild dolphins?

 When swimming, boating or snorkling in certain areas you can
 encounter wild dolphins. Keep in mind that in the US it is
 illegal to directly approach dolphins. If dolphins come
 towards you and choose to interact, that is allowed. Always
 check the local regulations for interactions with wildlife!
 In several areas there are boat operators that can take you
 to areas where there is a good chance to encounter dolphins
 (Florida, Bahamas, Hawaii, but also Norway and Iceland).

 A note of warning: there have been operators that have tried
 to lure dolphins by feeding them. This is illegal in the US
 and is highly undesirable, because it changes the dolphins'
 behavior. Currently there are operators offering bird-feeding
 tours. These bird feedings take place in areas frequented
 by dolphins and are an attempt to circumvent the dolphin
 feeding ban. Do not use these operators.

 Also note that there is some evidence that swimming with
 wild dolphins may change their behavior (Scarpaci et al, 2001)

 Source:
 C. Scarpaci, S.W. Bigger, P.J. Corkeron & D. Nugegoda (2001)
   Bottlenose dolphins (Tursiops truncatus) increase whistling
   in the presence of 'swim-with-dolphin' tour operations
   Journal of Cetacean Research and Management 2(3): 183-185


2.13 - Why do whales and dolphins beach themselves?

 If a single whale or dolphin strands, it usually is a very
 sick (and exhausted) animal. Such an animal often has some
 infections (pneumonia is almost always one of them) and a lot
 of parasites (worms in the nasal passages are very common).
 Sometimes these animals can be rehabilitated, but often they
 are so sick they won't make it.
 Some species of whales and dolphins occassionally strand in
 groups. A stranding of 2 or more animals is usually called a
 mass stranding. There are a number of theories that try to
 explain the occurrence of mass strandings. No theory can
 adequately explain all of them. In some cases it will be a
 combination of causes. The most common explanations are:
 - deep water animals (the species that most often are the
   victim of mass strandings) can not "see" a sloping sandy
   beach properly with its sonar. They detect the beach only
   when they are almost stranded already and they will panic
   and run aground.
   source:
   W.H. Dudok van Heel (1962):
     Sound and Cetacea. Neth. J. Sea Res. 1: 407-507
 - whales and dolphins may be navigating by the earth's
   magnetic field. When the magnetic field is disturbed (this
   occurs at certain locations) the animals get lost and may
   run into a beach.
   source:
   M. Klinowska (1985):
     Cetacean live stranding sites relate to geomagnetic
     topography. Aquatic Mammals 11(1): 27-32
 - in some highly social species, it may be that when the
   the group leader is sick and washes ashore, the other members
   try to stay close and eventually strand with the group leader.
   source:
   F.D. Robson (?)
   The way of the whale: why they strand.
   (unpublished manuscript)
 - when under severe stress or in panic, the animals may fall
   back to the behavior of their early ancestors and run to
   shore to find safety.
   source:
   F.G. Wood (1979)
   The cetacean stranding phenomena: a hypothesis.
   In: J.B. Geraci & D.J. St. Aubin: Biology of marine
   mammals: Insights through strandings. Marine Mammal
   Commission report no: MMC-77/13: pp. 129-188

2.14 - How deep can dolphins dive?

 The deepest dive ever recorded for a bottlenose dolphin was a
 300 meters (990 feet). This was accomplished by Tuffy, a
 dolphin trained by the US Navy. Most likely dolphins do not
 dive very deep, though. Many bottlenose dolphins live in fairly
 shallow water. In the Sarasota Bay area, the dolphins spend a
 considarable time in waters that are less than 2 meters
 (7 feet) deep. Other whale and dolphin species are able to
 dive to much greater depths even. The pilot whale
 (Globicephala melaena) can dive to at least 600 meters (2000
 feet) and a sperm whale (Physeter macrocephalus) has been found
 entangled in a cable at more that 900 meters (500 fathoms)
 depth. Recent studies on the behavior of belugas
 (Delphinapterus leucas) has revealed that they regulary dive
 to depths of 800 meters. The deepest dive recorded of a beluga
 was to 1250 meters.

 sources:
 F.G. Wood (1993)
   Marine mammals and man. R.B. Luce, Inc., Washington.
 E.J. Slijper (1979)
   Whales, 2nd edition. Cornell University Press, Ithaca, NY.
   (Revised re-issue of the 1958 publication: Walvissen, D.B.
   Centen, Amsterdam).
 R.S. Wells, A.B. Irvine & M.D. Scott (1980)
   The social ecology of inshore odontocetes. In: L.M. Herman
   (ed.): Cetacean Behavior. Mechanisms & functions,
   pp. 263-317. John Wiley & Sons, New York
 A.R. Martin (1996)
   Using satellite telemetry to aid the conservation and wise
   management of beluga (Delphinapterus leucas) populations
   subject to hunting.
   Paper presented at the 10th Annual Conference of the European
   Cetacean Society, March 11-13, 1996, Lisbon, Portugal.

2.15 - How fast can dolphins swim?

 The dolphin's fast cruising speed (a travelling speed they can
 maintain for quite a while) is about 3-3.5 m/s (6-7 knots,
 11-12.5 km/hr). They can reach speeds of up to 4.6 m/s
 (9.3 knots, 16.5 km/hr) while travelling in this fashion. When
 they move faster, they will start jumping clear of the water
 (porpoising). They are actually saving energy by jumping.
 When chased by a speedboat, dolphins have been clocked at
 speeds of 7.3 m/s (14.6 knots, 26.3 km/hr), which they
 maintained for about 1500 meters, leaping constantly.

 Energetic studies have shown, that the most efficient
 travelling speed for dolphins is between 1.67 and 2.27 m/s
 (3.3-4.5 knots, 6.0-8.2 km/hr).

 There have been reports of dolphins travelling at much higher
 speeds, but these refer to dolphins being pushed along by the
 bow wave of a speeding boat. They were getting a free ride
 (their speed relative to the surrounding water was low).
 A recent study using based on the vertical speed during
 jumps showed maximum speeds for bottlenose dolphins of
 8.2-11.2 m/s (16-22 knots, 29.5-40.3 km/hr) prior to a high
 jump. The maximum speed for wild bottlenose dolphins was
 5.7 m/s (11 knots, 20.5 km/hr) and for common dolphins
 6.7 m/s (13 knots, 24.1 km/hr).

 sources:
 D. Au & D. Weihs (1980)
   At high speeds dolphins save energy by leaping.
   Nature 284(5756): 548-550

 J.J.Rohr, F.E.Fish and J.W. Gilpatrick, Jr. (2002)
   Maximum swim speeds of captive and free-rangings
   delphinids: critical analysis of extraordinary
   performance
   Marine Mammal Science 18(1):1-19

 T.M.Williams, W.A.Friedl, J.A. Haun & N.K.Chun (1993)
   Balancing power and speed in bottlenose dolphins (Tursiops
   truncatus) in: I.L. Boyd (ed.): Marine Mammals -
   Advances in behavioural and  population biology,
   pp. 383-394. Symposia of the Zoological Society
   of London No. 66. Clarendon Press, Oxford

2.16 - Where can you find dolphins?

 Whales and dolphins can be found in almost every sea and ocean,
 from the Arctic ocean, through the tropics all the way to the
 Antarctic. Each species however has its own prefered type of
 habitat. Some live cold water only, others in tropical oceans
 only. There are also species that can be found in a large
 variety of environments, like the bottlenose dolphins, killer
 whales and sperm whales.

 source:
 P.G.H.Evans (1987)
   The Natural History of Whales and Dolphins.
   Christoper Helm Publishers, London.


2.17 - Can dolphins live in fresh water?

 There are a number of dolphin species that live in fresh water.
 They all belong to the river dolphin families. These are:
 the Platanistidae (Ganges and Indus river dolphins), the
 Iniidae (the boto or Amazon river dolphin) and the
 Pontoporiidae (the baiji and the franciscana). There is one
 species that can be found both in fresh water (the Amazon
 river) and in coastal sea waters: the tucuxi (Sotalia
 fluviatilis).
 In general, salt water species don't do well in fresh water.
 They can survive for some time, but they will be come
 exhausted (since they have less buoyancy in fresh water) and
 after a while their skin will start to slough (like our own
 skin after spending a long time in the bathtub).

 source:
 P.G.H.Evans (1987)
   The Natural History of Whales and Dolphins.
   Christoper Helm Publishers, London.

2.18 - How do dolphins get their water?

 Most dolphins live in the ocean and the ocean water is too
 salty for them to drink. If they would drink sea water, they
 would actually use more water trying to get rid of the salt
 than they drank in the first place. Most of their water they
 get from their food (fish and squid). Also, when they
 metabolize (burn) their fat, water is released in the process.
 Their kidneys are also adapted to retaining as much water as
 possible. Although they live in water, they have live as
 desert animals, since they have no direct source of drinkable
 water.

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