Larger Males

Representative Trantis said:

On the whole males are larger than females. The only exceptions are those animals which live close
together and therefore have increased competition between males for females.

I'm sceptical about this - can you cite any evidence for these exceptions?

Quoted message said:

Humans are a good example of this, so much so that we tend to think of all males being bigger.

Humans (And various primates) Bulls Dogs?

Does anyone know the complete list of species which have larger males, and if it's a big list then
a summary of many commonly known animals?

Textbooks should help too, especially ones on the evolution of
behaviour. Two of John Maynard Smith's books might help - either "The

some useful information /references. I don't have either to hand, so I'm afraid I can't check.

Bob

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Bob O'Hara

Rolf Nevanlinna Institute
P.O. Box 4 (Yliopistonkatu 5) FIN-00014 University of Helsinki Finland Telephone: +358-9-191 23743
Mobile: +358 50 599 0540 Fax: +358-9-191 22 779 WWW: rni.helsinki.fi~bohOpen ↗

Representative Trantis <[email hidden]> wrote:

: On the whole males are larger than females. The only exceptions are those animals which live close
: together and therefore have increased competition between males for females.

A better discussion of this:

``In the population of human beings males are, on average, considerably larger than females. In
fact, if you look around you this seems generally to be the case. Bulls are larger than cows,
stallions larger than mares, toms a bit larger than female cats and so on. The same general rule
seems to hold among birds.

Although it is generally true among mammals and birds that the male is bigger than the female
it is not in fact true for most living species. The reverse is generally true for insects,
fishes, amphibians and reptiles. Thus by numbers, most of the world's females are larger than
the males. [...]''

- helios.physics.uoguelph.cascor202.htmOpen ↗
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Representative Trantis <[email hidden]> wrote:

: On the whole males are larger than females. [...]

Questionable:

google.comsearchOpen ↗"females+are+larger+than+males" 1,780

google.comsearchOpen ↗"males+are+larger+than+females" 1,610

Males need to move around more than females - and females usually provide the nutritional supplies
for offspring.

Both factors tend to make the females bigger and the males smaller.

The cases where the males are bigger tend to involve male-male combat.
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in article [email hidden], Representative Trantis at
[email hidden] wrote on 9/7/03 4:19 PM:

Quoted message said:

On the whole males are larger than females. The only exceptions are those animals which live close
together and therefore have increased competition between males for females.

Did you mean to write that "On the whole FEMALES are larger than MALES?"

Guy

"Representative Trantis" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

On the whole males are larger than females. The only exceptions are those animals which live close
together and therefore have increased competition between males for females.

Strong competition between males for females is a major factor *promoting* large males.

Quoted message said:

Humans are a good example of this, so much so that we tend to think of all males being bigger.

Humans (And various primates) Bulls Dogs?

Does anyone know the complete list of species which have larger males, and if it's a big list then
a summary of many commonly known animals?

I don't know of a list, but I do know that the elephant seal has the

Because of a fundamental asymmetry between males and females, stemming from the initial asymmetry in
gamete size (anisogamy), females are a limiting resource and males are exploiters of this resource.
A mated female generally doesn't increase her number of offspring as she gets more matings, and
often matings are harmful for females. A male's success (number of offsrping) is, however,
approximately proportional to the number of matings he can get. This is Bateman's Law. It means that
females generally do not need to compete for males, but males generally need to compete for matings
with females. If winning fights allows a male to fertilise more females, and if being big helps a
male win more fights, then big males will tend to be favoured; hence the dimorphism.

There are exceptions though, because the above conditions will not always be fulfilled.

Representative Trantis said:

On the whole males are larger than females. The only exceptions are those animals which live close
together and therefore have increased competition between males for females.

Humans are a good example of this, so much so that we tend to think of all males being bigger.

Humans (And various primates) Bulls Dogs?

Does anyone know the complete list of species which have larger males, and if it's a big list then
a summary of many commonly known animals?

Most animals are insects. I believe that in the majority of insect species the female is larger than
the male. So on the whole, females are larger than males, I'm afraid. Try to escape from vertebrate-
centric bigotry!

Regarding the complete list of species with larger males, well, we don't have anything resembling a
complete list of any sort yet, so one

Best

Rob Knell

"Guy Hoelzer" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

in article [email hidden], Representative Trantis at [email hidden] wrote on 9/7/03
4:19 PM:

Quoted message said:

On the whole males are larger than females. The only exceptions are

those

Quoted message said:

Quoted message said:

animals which live close together and therefore have increased

competition

Quoted message said:

Quoted message said:

between males for females.

Did you mean to write that "On the whole FEMALES are larger than MALES?"

Guy

Sorry, yes I did, Sorry, I typed it very quickly. I shall try to be more carefull in future. :-)

Name And Address Supplied said:

"Representative Trantis" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

On the whole males are larger than females. The only exceptions are those animals which live close
together and therefore have increased competition between males for females.

Strong competition between males for females is a major factor *promoting* large males.

Quoted message said:

Humans are a good example of this, so much so that we tend to think of all males being bigger.

Humans (And various primates) Bulls Dogs?

Does anyone know the complete list of species which have larger males, and if it's a big list then
a summary of many commonly known animals?

I don't know of a list, but I do know that the elephant seal has the

Quoted message said:

Because of a fundamental asymmetry between males and females, stemming from the initial asymmetry
in gamete size (anisogamy), females are a limiting resource and males are exploiters of this
resource.

I can't see how this stems from anisogamy - at best I would guess that they are both due to the
female carrying the offspring. Pregnancy is the limiting factor, and this will affect mate
competition, and also

<snip bit where we agree>

Bob

--
Bob O'Hara

Rolf Nevanlinna Institute
P.O. Box 4 (Yliopistonkatu 5) FIN-00014 University of Helsinki Finland Telephone: +358-9-191 23743
Mobile: +358 50 599 0540 Fax: +358-9-191 22 779 WWW: rni.helsinki.fi~bohOpen ↗

"Anon." <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Name And Address Supplied said:

"Representative Trantis" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

On the whole males are larger than females. The only exceptions are those animals which live
close together and therefore have increased competition between males for females.

Strong competition between males for females is a major factor *promoting* large males.

Quoted message said:

Humans are a good example of this, so much so that we tend to think of all males being bigger.

Humans (And various primates) Bulls Dogs?

Does anyone know the complete list of species which have larger males, and if it's a big list
then a summary of many commonly known animals?

I don't know of a list, but I do know that the elephant seal has the

Quoted message said:

Quoted message said:

Because of a fundamental asymmetry between males and females, stemming from the initial
asymmetry in gamete size (anisogamy), females are a limiting resource and males are exploiters
of this resource.

I can't see how this stems from anisogamy - at best I would guess that they are both due to the
female carrying the offspring. Pregnancy is the limiting factor, and this will affect mate
competition, and also

Quoted message said:

Trivers showed that the initial asymmetry due to anisogamy selects for females to be the primary
carers in general. In the mammals, part of this care takes the form of 'pregnancy'. Yes, there are
parental investments in which the female makes the larger contribution other than anisogamy, and
yes, these all increase the sense in which the female is a resource to competed over, but the reason
that it is the female which makes these additional investments stems from the intial asymmetry of
anisogamy.

"Name And Address Supplied"

Quoted message said:

Yes, there are parental investments in which the female makes the larger contribution other than
anisogamy, and yes, these all increase the sense in which the female is a resource to competed
over, but the reason that it is the female which makes these additional investments stems from the
intial asymmetry of anisogamy.

Though in fish it is not unknown for the male to offer most parental care, whilst in many birds, and
also of course in humans, the father shares parental duties more or less equally with the mother.

In the case of fish, it seems that the abandonment theory might work. If one partner abandons the
offspring, the other has to choose between offering all the care, or leaving them to certain death.
Since with fish the mother expels unfertilised eggs, which the father then fertilises, she has most
opportunity to abandon and leave the male with all the hard work.

With birds, the chick demands an awful lot of parental care, and two-parent families have a definite
advantage over single mothers. The male is therfore compelled to offer parental care is he is to
have any hope of seeing his chicks survive.

Name And Address Supplied said:

"Anon." <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Name And Address Supplied wrote:

<snip>

Quoted message said:

Quoted message said:

I can't see how this stems from anisogamy - at best I would guess that they are both due to the
female carrying the offspring. Pregnancy is the limiting factor, and this will affect mate
competition, and also

Quoted message said:

Quoted message said:

Trivers showed that the initial asymmetry due to anisogamy selects for females to be the primary
carers in general.

OK, can you give me the reference, I'm interested in how he set this up
- did he assume anisogamy came first? It looks like a chicken-and-egg situation (incidentally, this
problem has now been solved:
<http://www.improb.com/airchives/paperair/volume9/v9i4/chicken_egg.html>), and I want to be
convinced that we do have the answer.

Bob

--
Bob O'Hara

Rolf Nevanlinna Institute
P.O. Box 4 (Yliopistonkatu 5) FIN-00014 University of Helsinki Finland Telephone: +358-9-191 23743
Mobile: +358 50 599 0540 Fax: +358-9-191 22 779 WWW: rni.helsinki.fi~bohOpen ↗

Malcolm <[email hidden]> wrote:
: "Name And Address Supplied"

:> Yes, there are parental investments in which the female makes the larger contribution other than
:> anisogamy, and yes, these all increase the sense in which the female is a resource to competed
:> over, but the reason that it is the female which makes these additional investments stems from
:> the intial asymmetry of anisogamy.
:
: Though in fish it is not unknown for the male to offer most parental care, whilst in many
: birds, and also of course in humans, the father shares parental duties more or less equally
: with the mother.

: In the case of fish, it seems that the abandonment theory might work. If one partner abandons the
: offspring, the other has to choose between offering all the care, or leaving them to certain
: death. Since with fish the mother expels unfertilised eggs, which the father then fertilises, she
: has most opportunity to abandon and leave the male with all the hard work.

Much the same model no doubt applies to the seahorse - where it is the male that becomes pregnant:

scienceinafrica.co.zashorse.htmOpen ↗
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Rob said:

Most animals are insects. I believe that in the majority of insect species the female is larger
than the male. So on the whole, females are larger than males, I'm afraid. Try to escape from vertebrate-
centric bigotry!

Dimorphic size reversal is not only characteristic of invertebrates. It occurs in vertebrates as
well, just not as frequently.

Two papers appeared in today's (Sept. 11, 2003) issue of Nature describing the

one of the papers' abstract. the authors write: "The largest females in this

and 150% the height of the largest males, which is unprecedented among birds and
terrestrial mammals."

The most relevant finding of the two papers is that animals that had originally tentatively been
given species status are now recognized to be gender differences. The two papers are:

L. HUYNEN, C. D. MILLAR2, R. P. & D. M. LAMBERT. "Nuclear DNA sequences detect species limits in
ancient moa" Nature 425, 175 - 178 (11 September 2003); doi:10.1038/nature01838

MICHAEL BUNCE, TREVOR H. WORTHY, TOM FORD, WILL HOPPITT, ESKE WILLERSLEV,

extinct New Zealand moa Dinornis" Nature 425, 172 - 175 (11 September 2003); doi:10.1038/nature01871

Wirt Atmar