Update note: some proponents
of the AAT/H have moved away from the idea that the aquatic phase was in
a salt water environment, but most still claim humans' sweat and tears
systems evolved as an aquatic feature, as an excretory system for salt.
This is a remarkable development, and demonstrates one of the reasons the
AAT isn't taken seriously by those who study the evidence.
If tears and sweat in humans are claimed to be due to an aquatic lifestyle and the
need to excrete salt, the aquatic lifestyle must have been in a salt water
A freshwater aquatic period would be no more or less
likely to produce these adaptations than a terrestrial lifestyle, so the
purported aquatic lifestyle doesn't explain the supposed adaptation of
sweat and tears as systems to excrete salt.
Of course the AAT/H proponents
are wrong about what the human sweat and tears systems can do, so that
just compounds their error.
Tears and the AAT/H
"Until evidence of other animals
shedding emotional tears is well documented, I will continue to maintain
that emotional tearing generally occurs only in humans.
I agree with Montagu's view that 'the shedding of tears as an accompaniment to emotional distress
has been attributed to other animals... The truth, however, appears to
be that while some of these animals may on occasion exhibit the evidences
of tears, this occurs very seldom, and is the exception rather than the
rule. ...Psychic weeping is not known to occur as a normal function in
any animal other than man.'" (William H. Frey 1985: 147. Crying: The
Mystery of Tears by William H. Frey, Ph.D. with Muriel Langseth. Minneapolis:
Some of you may recognize the
name of the quoted above; he's the guy Elaine Morgan correctly refers to
as "a leading present-day authority on the subject" (Morgan 1990: 98, The
Scars of Evolution).
Dr. Frey has done studies of emotional tears and
Morgan feels they support her theory.
Why she feels they support her is
rather inexplicable, once you look at the evidence, including the evidence
in the book which Morgan cites.
This particular AAT/H idea, initially
promoted by Morgan and since repeated many times by AAT/H proponents, is that emotional
tears are seen only in humans and aquatic animals (she cites Frey as proof
despite his conclusion, which I quoted just now) and they (and our sweat
glands) evolved as system to excrete salt.
To do this, she ignores
a basic principle of physiology I've described below in a section on homeostasis.
This section is in two parts:
this first part is specifically on evidence for emotional tears in non-human
The second deals with tears and what they contain, and what this
means in regard to the likelihood of tears being an excretion system.
Do Animals Shed Emotional Tears?
This is the title of chapter 14
in William Frey's book (Morgan cited it in The Scars of Evolution
but left off the main title, leaving only the sub-title, and also left
off Frey's co-writer). In it Frey looks at evidence, both scientific and
anecdotal, for emotional tearing in non-human animals.
His conclusion opened this page.
From Frey's Chapter 14: Do
Animals Shed Emotional Tears?
from pp. 135-139: "Some
Scientists Say Animals Cry Tears"
In this section Frey mentions
"several reports of animals shedding emotional tears -- or what were interpreted
as emotional tears -- in the scientific literature cannot be ignored."
Frey opens with Darwin's reports
of tears in Indian elephants. Frey also points out the information that
AAT/H proponents never seem to mention (even though it appears on the same page of
Expression of the Emotions in Man and Animals); that Darwin
reported contrary information from his correspondents in Ceylon, where
observations of recently captured elephants showed no tearing, and "the
native hunters asserted they had never observed elephants weeping".
Then Frey continues with reports
of other animals shedding tears: dogs and wolves (Cecil Reynolds 1925);
seal (Ronald M. Lockley 1966 Grey Seal, Common Seal); sea otter
(Georg W. Stellar); lab rats (red tears from Harderian glands [the same
types of glands that elephants have]) (John E. Harkness and Marcella D.
Ridgeway); and gorilla (Dian Fossey 1983 Gorillas in the Mist).
Note that already we see a
mix of aquatic and non-aquatic animals mentioned; this will be a repeating
theme, as you'll see.
Another recurring theme, and the reason Frey ultimately
does not accept these reports as documented, is that none of these reports,
indeed none of the "pro-tears" reports, have any means of determining that
these tears are due to emotion rather than stress or irritation.
In any event, this already destroys the AAT/H claim that only aquatic animals have
been reported shedding emotional tears.
It should also be noted that
Frey's book was cited by Morgan, who nevertheless somehow managed to skip
all the reports of non-aquatic animals, despite the fact that they are
interspersed with the reports of tears in aquatic animals, just as they
are in my list in the paragraph above.
from pp. 139-141: "What
Animal Experts Say"
In this section, Frey and his
co-writer sent out questionnaires to zoos, animal parks, and marine parks,
veterinarians, etc., to see if any of them reported ever seeing emotional
tears in nonhuman animals.
Brian Davies, "an animal protectionist
and executive director of the International Fund for Animal Welfare" (he's
written two books protesting the harp seal hunts in Canada) says yes for
seals. Wayne Franzen, trainer of Okha (an Indian elephant), and co-owner
of Franzen Brothers Circus, says yes for Indian elephant.
Ian Douglas-Hamilton, "who
has done extensive studies of African elephants replied, 'I cannot say
that I observed emotional tears in African elephants, although I have seen
tears appear when they have been shot or wounded.
It is possible that these
may be related to emotion, but I am sorry to say I really do not have enough
observation in this to say one way or the other'."
Frederick A. King, director
of Yerkes Primate Center in Atlanta and survey of 5 experienced primate
scientists there say no.
The following experts were
asked "(1) Have you ever seen nonhuman animals shed emotional tears? and
(2) Do you know of any documented evidence of nonhuman animals shedding
emotional tears?" Saul Kitchener, director of the San Francisco Zoological
Park; R.M. McNorman, assistant curator of mammals, Bronx Zoo; G. Styfer,
overseer at the Toronto Zoological Park; Donald L. Jansen, DVM, associate
veterinarian at the San Diego Wild Animal Park; Sanford Friedman, curator
and chairman of mammal department at the Brookfield Zoological Park in
Illinois "all responded no to both questions".
"Veterinarians and animal trainers
who have worked extensively with seals, dolphins, and whales at Sea World
in Orlando, Florida, the Seaquarium in Miami, Florida, Marineland in Los
Angeles, California, and the Como Park Zoo in St. Paul, Minnesota" all
As they report, "seals, dolphins, and whales secrete a watery
mucus to protect their eyes from sea water.
The overflow of tears due to
lack of a drainage system may have been misconstrued as emotional tears".
from pp. 141-146: "Other
Reports of Animals' Tears"
Finally, since his earlier
work was written about in Psychology Today, Frey has gotten many
anecdotal reports about pets or other animals shedding tears.
include dogs, cats, cows, pigs, lambs, horse, and a kangaroo.
So we can see that there is
every bit as much, and as little, evidence for non-aquatic animals shedding
emotional tears as there is for aquatic animals.
This is contrary to Morgan's
claims in print, as well as the claims Morgan and others have made repeatedly
in the sci.anthropology.paleo newsgroup and other online forums.
We also see still more evidence
of Morgan's style, deliberately burying contrary evidence that is in a
book which she cites.
(Unless we are to believe that when she read Frey's
book, she didn't read the chapter entitled "Do Animals Shed Emotional Tears?"
-- does anyone believe that's likely?)
This second part deals with
tears and what they contain, and what this means in regard to the likelihood
of tears being an excretion system.
When Morgan cites William Frey's
work as support for the AAT/H; her reasoning is twofold:
1. She claims that emotional
tears are shed by humans, aquatic animals, and Indian elephants, and by
no other animals.
Part one of my post showed that the evidence for this
does not exist.
There are no documented cases of emotional tears being
shed by any nonhuman animal, and though there are anecdotal reports of
such tears in nonhuman animals, these report such tears in many non-aquatic
So it cannot be said to be a trait shared only by humans, aquatic
animals, and Indian elephants.
2. Frey's work demonstrates
that emotional tears do serve an excretory function, and Morgan claims
that the original function of emotional tears was the elimination of salt.
First we have an interesting
point; then we have to clear up some confusion introduced by Morgan's inaccurate
The point is that the composition
of human tears does show an excretory function of tears which sheds
light on their environment of origin.
This feature of tears, that they
are excretory in regard to some elements, was known even before Frey's
The actual composition of tears, as opposed to some imagined or postulated
composition, is not favorable to the AAT/H, but we'll come to that at the
The problem is the confusion
Morgan has introduced regarding the types of tears.
She uses the term "psychic
tears", and posits these as being one of two types of tears, the other
She claims there is "general agreement on this", but in
fact she is confused.
The two types of tears are "basic" (now generally
called "basal" or "continuous" tears) and "reflex" tears, and there is
in fact general agreement on this.
Emotional, also called "psychogenic",
tears are one form of reflex tears.
The stimulus is emotional rather than
Basal tears are the normal tear contribution to
the "tear film" which lubricates the eye.
"Reflex secretion may be of
sensory origin through fifth nerve stimulation (cornea, conjunctiva,
skin, nose) or of
central sensory origin. In the latter the stimulation
may be retinal, varying with the intensity of light, or psychogenic, as
in weeping caused by emotional disturbances or by various central nervous
The production of tears on an emotional basis is unique
to humans among all vertebrates". (Benjamin Milder 1987:24)
The excretory abilities of the lacrimal (tear)
It is an established physiological
fact that to be involved in changing the body's balance of a substance,
such as salt (the balance in what we are talking about is the balance of
water to a given substance), any given excretion must contain a concentration
of the substance that is greater than its concentration in plasma, which
is called being "hypertonic".
An organ which does this is said to be capable
of "active" rather than "passive" excretion for that substance.
lacrimal glands can and do perform active excretion is well known to those
in the field of ophthalmology.
However, they are not capable of actively
excreting sodium, as the AAT/H requires.
Central to Morgan's thesis
is that our lacrimal glands actively excreted salt at some time in the
past, even though they don't now.
This requires that our lacrimal glands
underwent two massive changes, starting and ending with a passive secretion
This idea is certainly far less parsimonious than the idea that
the observed and measured active secretion of the lacrimal gland indicates
our actual environmental past habitat.
Secretions in tears
The facts on substances which
the lacrimal gland is capable of actively excreting, and on sodium, which
the lacrimal gland cannot concentrate sufficiently for active excretion.
"Sodium in tears is about equal
to that in plasma and has been found to correlate with it, suggesting a
passive secretion into the tears.
"Potassium, with an average
value of about 20 mmol/l is much higher than the corresponding plasma concentration
of about 5 mmol/l. This indicates an active secretion into the tears".
(van Haeringen 1981:92)
"The manganese concentration
of emotional tears (25.2 +/- 6.6 ng/ml) was not significantly different
from that of irritant-induced tears (34.2 +/- 8.8 ng/ml) obtained from
the same healthy female subjects". (Frey et al. 1981:564)
"The manganese concentration
of emotional tears from women exceeded that of serum (0.98 +/- 0.09 ng/ml)
obtained from the same subjects by about 30-fold". (Frey et al. 1981:564)
"Paired samples from 25 women
also showed that the protein concentration of emotional tears was 24% greater
than that of irritant-induced tears (P<.01) (Table 1).
We found a higher
protein concentration for emotional tears from men as well (P>.05), although
we obtained paired samples from only four subjects". (Frey et al. 1981:562)
The only higher concentrations
that Frey and his colleagues found being excreted in emotional tears as
contrasted to irritant-induced tears were higher concentrations of proteins.
Frey feels that the process of crying helps in emotional release through
eliminating substances such as prolactin, ACTH, Leucine-Enkephalin, and
He also feels that the levels of prolactin in one's system provide
a threshold effect, affecting how easily emotional tears are shed in response
to a given stimulus. This, he thinks, accounts for his findings that women
"shed tears more often and more readily than men".
Adult women typically
have much higher levels of prolactin than adult males, and these levels
also rise during pregnancy, another period when emotional tears are known
to be more easily shed.
Innervation of tear secretion
Morgan has suggested that the
source of control for psychogenic tearing is important to her theory, but
this is based on her mistaken idea that human emotional tearing is a characteristic
shared by aquatic animals and no other animals.
This has been shown to
be a completely unsupported notion: there is no documented evidence for
nonhuman aquatic animals shedding emotional tears, and the anecdotal and
non-documented evidence is at least as strong or stronger for emotional
tears in non-aquatic nonhuman animals.
What matters is the ability
of lacrimal glands to excrete hypertonic substances. If they cannot excrete
a given substance with a greater concentration than it appears in plasma
(i.e., "hypertonic"), the purpose for these tears cannot be for excretion
of an excess of that substance. It is well documented that human tears
are never hypertonic in regard to sodium.
Tears are, however, strongly
hypertonic in regard to potassium. In this regard, the lacrimal glands
call to mind the "salt" glands of terrestrial reptiles and birds.
has many times -- both in published work and online -- inaccurately claimed
that salt glands are only found in marine birds and reptiles, ignoring
the many terrestrial birds and reptiles who have these glands. These animals
include ostriches and other birds, and lizards, including iguanas, chuckwallas,
The "salt" glands of these terrestrial birds and reptiles,
unlike those found in marine birds and reptiles, are used primarily to
"In other words the secretion resembles that of the
ostrich and differs markedly in composition from that of marine birds and
reptiles" (Peaker and Linzell 1975:247-8).
So the actual observed and
measured excretions in human tears far more closely resemble the excretions
from the "salt" glands of terrestrial birds and reptiles than those of
marine birds and reptiles.
Thus for human tears' excretory abilities to
indicate a terrestrial background requires no change.
For their abilities
to indicate a marine background requires not just one but two massive changes,
starting and ending with a passive secretion of sodium.
The idea that human tears indicate
a marine past is certainly far less parsimonious than the idea that the
actual observed and measured active secretion of the lacrimal gland indicates
our actual environmental past habitat would be terrestrial rather than
1975 Salt Glands in Birds and
Reptiles by M. Peaker and J.L. Linzell (Dept. of Physiology, Agricultural
Research Council, Institute of Animal Physiology, Babraham, Cambridge).
Monographs of the Physiological Society No. 32. Cambridge University Press:
Cambridge, London, New York, Melbourne.
1981 "Clinical Biochemistry
of Tears" by N.J. van Haeringen, Ph.D. Survey of Ophthalmology 26(2):84-96.
1981 "Effect of stimulus on
the chemical composition of human tears" by William H. Frey II, Ph.D.,
Denise DeSota-Johnson, B.A., and Carrie Hoffman, B.S.; and John T. McCall,
American Journal of Ophthalmology 92:559-567.
1985 Crying: The Mystery
of Tears by William H. Frey II, Ph.D. with Muriel Langseth. Minneapolis:
1987 "Chapter 2: The lacrimal
apparatus" by Benjamin Milder, M.D. In Adler's Physiology of the Eye:
Clinical Application, edited by Robert A. Moses, M.D. and William M.
Hart, Jr., M.D., Ph.D. Eighth edition. The C.V. Mosby Company: St. Louis,
Washington, D.C., and Toronto.
Homeostasis in bodily fluids refers
to a self-regulating process wherein an organism maintains, within reasonable
limits, a relatively steady balance of a given substance.
the most important of these is salt.
Our plasma contains salt, and we need a certain amount
of it or we get sick or die.
This is not just true of blood plasma, but the fluid (cytoplasm) in all our cells.
This isn't due to aquatic or non-aquatic
lifestyles, it's common to all vertebrates.
(Its only connection
to aquaticness is that it's almost certainly a holdover from the extremely
ancient past of hundreds of million of years ago when there actually were
nothing but aquatic animals.)
If we get too much salt in those fluids,
we have to be able to get rid of some or we get sick or die.
This also is true of all vertebrates, terrestrial and aquatic.
in bodily fluids doesn't just pertain to salt and water; other elements,
like potassium, are involved too.
The AAT/H often focuses on this process
because how these systems work in different animals does say a lot about
the environmental backgrounds over their evolutionary history.
They are right to look at it, but sadly, they generally seem to lack a basic
understanding of the physiology behind it, which leads them to make huge
Our method of maintaining balance in both salt and potassium,
when compared to aquatic and terrestrial mammals, does indeed point to
one of the two environments as the one we evolved in.
But it isn't
It is an established physiological
fact that to be involved in changing the body's balance of a substance,
such as salt or potassium (the balance in what we are talking about is
the balance of water to a given substance), any given excretion must contain
a concentration of the substance that is greater than its concentration
in plasma, which is called being "hypertonic".
An organ which does this
is said to be capable of "active" rather than "passive" excretion for that
For example, while AAT/H proponents claim we used our sweat glands
and tears to excrete salt, they are not capable, or even close to being
capable, of active secretion.
This is true of all mammals, including
Only one organ in mammals is capable of actively
excreting salt, the kidneys.
This is why the kidneys of marine mammals
are all large and heavily lobed, unlike human kidneys; with better hormonal control over rate of urine formation and concentration via the kidneys.
aquatic marine environment, there is one other environment which needs
this type of adaptation, and that, ironically, is very dry deserts.
The problem in both places is the same, little or no fresh water, and the
denizens thereof must be able to conserve the water they get and expel
the salt they get with it.
So kangaroo rats and whales turn out to
have a lot in common, homeostasis-wise.
Note that when I pointed
this out in the sci.anthropology.paleo newsgroup, some AAT/H proponents (including
Elaine Morgan) couldn't see why we would use the same system that every
other mammal uses, without exception.
Because birds' and reptiles'
kidneys are not as highly developed as those of mammals, they have had
to develop the salt glands that AAT/H proponents think we should've emulated.
Remember that an organism can't just evolve whatever feature it likes,
like picking up a performance muffler and installing it on your car.
They start with what they have, and birds and reptiles have kidneys which
are inefficient compared to those of mammals.
In fact, the more sophisticated
kidney is considered to be one of the great mammalian adaptations.
All mammals faced with high salt loads relative to fresh water availability,
have developed specialized kidneys to deal with the problem, kidneys which
can produce highly concentrated urine.
Humans do not have these features.
Aquatic mammals, in fact, can even get necessary water by drinking seawater
for an indefinite period; humans doing so get sick and die.
mammals actually generally get enough water through their food, which is
also about as salty as seawater.)
Besides the simple yet critical
matter of sweating being entirely incapable of producing the required hypertonic
salt-water mix -- it's never even close to hypertonic -- there is another
critical reason that sweating (whether eccrine or apocrine) is not a usable
salt excretion system: its essentially unregulated nature (the mammalian
renal system, on the other hand, is a highly regulated system whose purpose
is the regulated excretion of various substances and the maintenance of
the required salt-water balance).
If you simply sweat a lot and drink
fresh water, under work stress the renal system can shut down.
This causes a health crisis, with accompanying violent and painful cramps, as well
as -- less immediately dangerous but still critical -- fatigue and depression.
This would make relying on "sweating plus drinking water" a highly dangerous
form of salt excretion, even if the required large amounts of drinking
water are available.
How large would these amounts of water be?
Assume for a moment that you don't mind violent cramps
on a daily basis, and that they wouldn't be a problem for an aquatic mammal.
How much would you have to sweat to sweat out this salt?
researchers had the idea that sweat might be a excretory process rather
than the one which tends to retain as much non-water as possible.
They of course realized that salt was far too dilute in sweat for it to
be a target of this hypothesized excretory system; they went for urea as
However, researchers J.S. Weiner and K. Hellman pointed
out that the sweat glands' activity "is directed quite to the opposite
purpose, of conserving sodium chloride and glucose" (1960:171) and they
did the calculations to see how much sweat would be required to perform
this task: the number is 80 liters.
80 liters of sweat every day,
and the upper limit for men working all day in desert conditions (far more
strenuous and harsh conditions than our hominid ancestors would go through)
is 10 liters (6 liters being the more normal amount under those harsh conditions).
Clearly, sweat just can't be expected to do the job, and keep in mind that
urea is far more plentiful in sweat than salt is.
And even if you
could sweat more than 80 liters a day, every day, there's those violent
Sweat as an excretory system just doesn't make sense at all.
By the way, all this info was available long before even Hardy wrote up
his AAT/H paper; even longer before Morgan did her first book on the subject.
Was Morgan aware of it?
I got the reference to Weiner and Hellman's
research from her; she quoted them. So she had the info in her hand that proved her
contention to be wrong even as she wrote it up.
Organisms which rely on maintaining
a salt-water balance (all vertebrates except for some fish) must have a
regulated system which doesn't simply "mess up" their salt-water balance.
This isn't just a nicety, or a handy option in life; it's a critically
important need without which the organism cannot live.
this system is always, without exception, the renal system; it is never,
ever, any other system... period.
Other types of vertebrates utilize
other systems -- gills, salt glands, or the skin itself -- but mammals
always use the kidneys.
This is not opinion or hypothesis, but basic physiological fact.
1988 Animal Physiology:
Mechanisms and Adaptations (3rd edition) by Roger Eckert (University
of California, Los Angeles), with Chapters 13 and 14 by David Randall (University
of British Columbia), revised in part by George Augustine (University of
W.H. Freeman and Company: New York.
The Vertebrate Kidney
To speak of the vertebrate
kidney would be misleading unless we note that it is organized somewhat
differently in different groups of vertebrates.
Comparisons can be made
after we first consider the mammalian kidney.
The mammalian kidney performs
certain functions that in lower vertebrates are shared by such organs as
the skin and bladder of amphibians, the gills of fishes, and the salt glands
of birds and reptiles.
It is also the osmoregulatory organ of which we
have the most complete understanding, thanks to extensive research over
the past four to five decades.
Salt glands have subsequently
been described in many species of birds and reptiles, especially those
subjected to the osmotic stress of a marine or desert environment.
These species include nearly all marine birds, ostriches, the marine iguana,
sea snakes, and marine turtles, as well as many terrestrial reptiles.
Crocodilians have a similar salt-secreting gland in the tongue.
The formation of nasal
gland fluid does not include filtration, as does the formation of urine
by the glomerular kidney.
1978 Comparative Anatomy
of the Vertebrates (4th edition) by George C. Kent (Department of Zoology
and Physiology, Louisiana State University, Baton Rouge, Louisiana). C.V.
Mosby Co.: Saint Louis.
Sweat glands eliminate
some salt in mammals, but salt loss by this route is merely incidental
to secretion of water for its evaporative cooling effect. It is not a regulated
route for salt excretion and, in fact, salt lost by this route usually
must be replaced. Mammals eliminate excess salt via kidney tubules.
1990 Sea Otters by Marianne
Riedmann. Monterey Bay Aquarium: Monterey, California
Otters and most other
marine mammals are constantly in danger of losing water to the more concentrated,
or salty, ocean in which they live.
They must keep the osmotic concentration
of their body fluids constant despite their saltwater environment, a process
known as osmoregulation.
And besides living in sea water, sea otters
eat marine invertebrates that have an elevated salt content, much higher
than that of fishes, and often as high as that of the surrounding sea water.
This salty diet raises the otter's "salt load" even further.
Sea otters conserve water and maintain a suitable water balance by means of
their large, heavily lobulated kidneys. Their kidneys are very efficient
at concentrating urine by absorbing water and eliminating excess salt in
urea, a waste product that's more concentrated than ocean water. Yet exhibit
otters living at the aquarium sometimes drink fresh water from a hose and
sprinklers that clean the windows. Although wild otters lack sources of
fresh water, they do drink sea water, which may help them process and eliminate
1990 The Pinnipeds: Seals,
Sea Lions, and Walruses by Marianne Riedmann. University of California
Press: Berkeley, L.A., and Oxford.
water and maintain water balance in several ways. The heavily lobulated
kidneys of seals and most marine mammals are extremely efficient at concentrating
urine; they absorb water and eliminate excess salt in urine that has a
concentration equal to or greater than seawater [various refs that I didn't
copy]. The chloride concentration in seal urine is therefore as high as
or higher than that of ocean water (which contains an average of 535 millimoles
of chloride per liter). A seal that drinks a liter of seawater, after excreting
the salts, ends up with a slight net gain of pure water. A human, however,
experiences a net water loss of about a third of a liter of water after
drinking the same amount of seawater. Human kidneys are less powerful than
those of seals or whales, and even the most concentrated urine they can
produce is always more dilute than salt water. Water is therefore wasted
in eliminating the excess salt in urine.
1984 Grzimek's Animal Life
Encyclopedia vol 11: Mammal II Dr. Bernhard Grzimek, ed. Van Nostrand
Reinhold: New York, Cincinnati, Toronto, London, Melbourne
"Whales" by Dr. Everhard J.
Slijper (Professor, Zoological Laboratory, University of Amsterdam) and
Dr. Dietrich Heinemann (Director, Zoological Garden, Munster)
pg. 462, 467 (pages 463-466
are not really built for an aquatic life; the salt content of their blood
and body tissues is less than that of sea water.
Thus the excess
salt which is accumulated from food and water must be eliminated from the
Whales do not have salt excretory cells like those the bone fishes
have on their gills.
They are not able to excrete salt through their nasal
glands like many sea birds.
Whales also do not have perspiration glands,
which help many other mammals give off excess salt.
The kidneys are the whale's only salt-excreting organs.
Whales have very large kidneys relative
to those of land mammals; the kidneys of small whales are twice as large
as those in land mammals of the same size.
In addition, the whale's kidneys
are divided into several lobes, the renculi, so that the important exterior
surface is increased.
Whales are probably able to excrete large quantities
of urine with their kidneys.
We do know that the urine of the bottle-nosed
dolphin occasionally contains particularly large amounts of salt.