Have you tried Copepods? I know that Benni Winding Hansen published a lot papers about copepods life traints and reproductions.

Hello David,

the sperm whale is certainly one of the species you're looking for. In fact, the sperm whale is an animal of extreme sexual dimorphism, where mature males, measuring up to 18 meters, have almost double the length of a mature female and three times the mass.

Pinnipeds also show considerable size dimorphism. Elephant seals are one example.

Yes, most (all?) of the examples are the opposite, energetic requirements for reproduction see to be the major driver (sperm are cheap!), a related question that may be of interest is progressive hemaphroditism (protogynous, protandrous) where most often the larger/older individuals are female, but some (groupers for example) change to male as they get older, Ive always been curious about what drives that.

Are you looking for only invertebrates? If not lots pinnipeds and whales have the kind of size difference you are looking forp.Also protgynous fish like for example labrids may show larger male size.

Birds also have some examples of sexual size dimorphism, although they are generally more modest than in fish or spiders. One good example is the great bustard where males can weigh 2 to 3 times that of females.

For marine mammals you may want to start from here, the file has a good summury of sexual simoephism including size dimorphism

As others have suggested pinnipeds (seals and sea lions) are classic examples of very large males compared to females. These are a couple of references with data on body size and sexual dimorphism in pinnipeds

Fitzpatrick J.L., Almbro M., Gonzalez-Voyer A., Hamada S., Pennington C., Scanlan J., Kolm N. 2012 Sexual selection uncouples the evolution of brain and body size in pinnipeds. Journal of Evolutionary Biology 25, 1321-1330. (doi: 10.1111/j.1420-9101.2012.02520.x).

Lindenfors P., Tullberg B., Biuw M. 2002 Phylogenetic analyses of sexual selection and sexual size dimorphism in pinnipeds. Behavioral ecology and sociobiology 52, 188-193. (doi: 10.1007/s00265-002-0507-x).

I would look at those species with a harem mating system - it would make sense that the males are much larger in order to fend off competition from other males, e.g. elephant seals.

Not all fish species have smaller males. For instanse, male capelin Mallotus villosus are much greater than females.

Wrasse: many species of wrasse start life as females. When the local male is lost, it tends to be the largest female in the group that changes sex and becomes the local male. Hence male wrasse tend to be larger than female wrasse. The cuckoo wrasse is a prime example, where this is really obvious. Male cuckoo wrasse are invariable larger than female fis.

There are many examples, especially amongst mammals and as some other contributors here state, particularly amongst pinnipeds. Southern elephant seals are the most sexually dimorphic mammals on earth, adult males sometimes weighing as much as 10 times what adult females do.

As Aleksandra said, any species where males defend harems of females (i.e. female defense polygyny mating system) tend to have larger males. This is true of quite a few fish species (parrotfishes and wrasses), several pinnipeds, deer (red deer), and some siphonoecetine amphipods.

This may be a useful book too

Charnov, E. L. (1982). The theory of Sex Allocation. Monographs in Population Biology, Princeton University Press, Princeton, New Jersey

The echiurid Bonellia viridis!

The femal is 10-15 long (with a extensible feeding proboscis up to 1-1,5 m long) while the male is difficult to observe being 1-3 mm

In some red seaweed, the gametophytes (haploid plants), and mainly the female plants are smaller or present growth reduced in relationn to the diploid or sporophyte plants.

Examples in fish: species which are protogynous hermaphrodites, i.e. small individuals are female and then transform into males. This includes wrasses, as already mentioned, and other fish such as groupers.

Many examples in http://en.wikipedia.org/wiki/Protogynous_hermaphrodite#Protogyny

Example in parasites: the blood fluke Schistosoma, in which the small female lives within the gynaecophoric canal of the male. This is an exceptional case in parasites; in most cases females are larger than males.

I am aware of the mammalian examples and the fact that it is only some fish where the males are very small. However, the dimorphism in pinnipeds is minor compared to the four orders of magnitude exhibited by red algae in Palmariales where the female might only undergo a few cell divisions before producing her single female gamete. The male thallus may be 50 cm long and perennial.

The Fathead minnow (Pimephales promelas). The male is approx 1.5 to 2 times larger than the female and it is the male that defends the nest and cares for the eggs.

Snappers are one example where males (by necessity) are larger than females. All snappers are females when small and then some change into males.

Northern Fur Seals, Callorhinus ursinus

yes, pinnipeds come to mind. check out Zalophus californianus (California sea lions) for one.

Elephants exhibit pronounced sexual dimorphism - large adult males can be double the weight of an adult female.

If your question refers to size difference as they grow older, then brown crab (Callinectes bellicosus) -as most crabs-, is an example. Although there is some debate, apparently, most females stop molting once they mature and develop egg mass, therefore they do not grow any longer.

See:

Rodríguez-Domínguez, G., S.G. Castillo-Vargasmachuca, R. Pérez-González & E.A. Aragón-Noriega. 2012. Estimation of the individual growth parameters of the brown crab Callinectes bellicosus (Brachyura, Portunidae) using a multi-model approach. Crustaceana 85(1): 55-69.

Some marine mammals as Zalophus califronianus, Otaria byronia or Mirounga angustirrostris are perfect examples of those differences.

There are quite a few examples of Sexual dimorphism where male size is greater than female size:

In the animal kingdom (Kingdom Animalia) the Male Common Pheasant is much bigger than the female [http://en.wikipedia.org/wiki/File:Male_and_female_pheasant.jpg]

http://en.wikipedia.org/wiki/Sexual_dimorphism

The pinnipeds mentioned above probably have the largest difference in size between adult females and males but ungulates such as caribou, deer, moose and elk have males that are much larger than the females.

In several squid species, and maybe in other cephalopods, exist sexual dimorphism (size difference between males and females) but generally the females are bigger than the males.

In protogynous hermaphrodites large male size ensures mating success - the size advantage hypothesis. Large size and (at least in fishes) bright colouration in males are typical characterstics of these species. For example members of the Family Labridae (one of the most diverse fish families) are protogynous hermaphrodites. This family includes the parrotfishes (approx 90 species) and in this group males are typically more colourful and larger than females. In the parrotfish Scarus ferrugineus females reach 26- 27 cm, while males reach 35 - 36 cm.

Snow crab Chionocetes opilio is widely distributed and commercially significant crab species. Males are approximately twice larger than females.

In case of Phylum Echuroidea, bonelid worms are included. In these organisms females are of bigger size, sedentary but males are like tiny worm like with cilia and motile. Such organisms found in the littoral zone.

I could also point you to Cephalopods specifically the species of small squid Alloteuthis subulata (loligo media) where the mature males have an extraordinarily long extension of the mantle which means they have more than twice the body length of mature females.

Yes, echiurids are a good example, especially Bonellia viridus free-living females of which achieve a length of 1,5 m, mostly by the length of the proboscis, while parasitic males are 200,000 times smaller. Another similar case are deep water ceratioid anglerfishes whose semiparasitic males are 75 times shorter than their free-living females and 500,000 times smaller in weight.

See: Jaccarini, V. et al. 1983. J. Exp. Mar. Biol. Ecol. 66: 25-40.

Pietsch, T.W. 2005. Ichthyol. Res. 52: 207-36.

Amphipods (Crustacea) are another example. So much so, that males (of certain superfamilies) use their size to literally carry their mates until they are ready to molt and be fertilized (amplexis or precopulatory guarding).

See:

Conlan (1991). Hydrobiologia 223:255-282.

Ward (1983). Behavioral Ecology and Sociobiology 14:69-76.

Wellborn and Bartholf (2005). Oecologia 143:308-316.

The males of the African bullfrog (Pyxicephalus adspersus) are notably bigger than the females, which is unusual (?unique?) amongst frogs.

In parasitic organisms, and particularly trematodes, the Schistosomatidae presents an instructive case. Parasites are gonochoric instead of being hermaphrodites. The female is at least as long as the male but his body is extremely thin. It totally depends on the male to provide transportation within the circulatory system of vertebrate hosts. The male has a gynecophoric canal which houses the female. Studies have shown that female sexual maturation occurs only after pairing.

Dr Gabriel Mouahid

Hi David,

Many crustaceans have larger males.... But the interesting part about your question is that there is not only the size difference but also the growth-rate difference. Does this translate into different longevity? Perhaps different reproductive patterns (iteroparus vs semeloparus)?

Maybe even too trivial to mention, but in most mammal species where males compete for females by displays and ritualized (or not so ritualized) fights, you will find quite shocking sexual dimorphism. Elephant seals, elephants, lions, bears, apes...just to mention some of the most charismatic taxa.

in Homo sapiens specie the difference in size also occurs....and thats could possibly bring some sexual problems during mating...

Hi David- I believe some seahorses are sexually dimorphic with larger males

Hi David,

As pointed out by several answers, there are several examples of species in which males are larger than females. The question however is a very interesting one when it comes to look for explanations.

A very interesting paper on the subject is that of Webb and Freckleton (2007) dealing with Sexual Size Dimorphism (SSD) and Rensch's rule, that states that sexual dimorphism increases with body size. They highlighted the fact that in taxa where males are larger than females (male-biased SSD, MBSSD), SSD does indeed tend to increase with body size. Yet, in taxa with female-biased SSD (FBSSD) which is indeed the most prevalent direction of dimorphism, evidence for Rensch's rule (i.e., that SSD should decrease with body size) is extremely scarce. I would strongly suggest that you read their paper (based upon the study of 1291 species of birds across 30 families), and some references therein for a very straightforward discussion on this point. Note that one of their conclusions is that "unlike several other ecological scaling relationships, Rensch's rule does not exist as an independent scaling phenomenon". At least for birds.

Hope this helps,

Tito

Webb, T.J. & Freckleton, R.P. (2007) Only Half Right: Species with Female-Biased Sexual Size Dimorphism Consistently Break Rensch’s Rule. PLoS ONE, 2, e897.

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000897

Hi all,

One more point to follow up with Fernando's mention of Homo sapiens. It does not seem that male Homo sapiens being that bigger than females. Notwhitstanding the obvious fact that men, on average, are about 15 percent to 20 percent larger than women. When compared with other mammals (chimps and gorilla for instance), that margin is narrow. And this point could be related to the acquiring of monogamy. Yet controversial, and somewhat away of the current topic of David's question, this point is a very interesting one when it comes to anthropology.

Please read:

Philip L. Reno, Richard S. Meindl, Melanie A. McCollum, and C. Owen Lovejoy. Sexual dimorphism in Australopithecus afarensis was similar to that of modern humans PNAS 2003 100 (16) 9404-9409; doi:10.1073/pnas.1133180100

Cheers,

Tito

I would like to thank everyone for their responses and especially for the references. Unless I have missed a few for the remarks, Palmariales does seem to be an extreme example of diminutive females. There is an issue of longevity here. The females are fertile very soon after the spores germinates, and will produce a single egg. If the egg is fertilized, the zygote develops directly and overgrows the female. Accordingly, females are fertilized by males that have been growing for at least a year. The adaptation may have a simple explanation in that it avoids inbreeding in that it makes it difficult for the meiotic products from a single thallus to eventually produce haploid thalli that can interbreed. I suspect that many of the animal examples (i.e. small males) may come down to such an explanation as well. This is also an example of extreme K-selection; however, that zygote grows into a plant that produces 100s of thousands of eventual spores.

By the way, in general, in red algae where separate thalli produce the gametes, the plants are usually the same size or the male is smaller.

Some species of chelonia (giant tortoises), as well as the larger crocodilians have size differences of several hundred pounds between the sexes when mature. The typical male Aldabra tortoise generally weighs around 500-600lbs whereas the females are about 200, and the American Alligator can reach legnths of 12-14 feet, 800-1000lbs with the record length of 19' for a male, and females maxing out around 9' and about 300lbs.

Many of the shell spawning species of cichlid (Neolamprologus species) from Lake Tanganyika in Africa have small females that are able to inhabit snail shells. The larger males fertilise the eggs laid within the shell externally and are to large to access the shell. There may well be species that occupy a similar niche in the marine environment, although non spring to mind but check out blennies and gobies to start with. You may turn up something useful.

Hi David,

I read about this book that is expected to be out in next April 2013:

Odd Couples: Extraordinary differences between the sexes in the animal kingdom by Daphne J.Fairbairn

Published by: Princeton University Press.

As I understand reading the New Scientist's presentation of the book, it deals with the "striking distinctions among sexes". I expect it to be very interesting regarding the issue discussed here and I am looking forward with eager expectation reading this book !

Cheers

Tito

PS: you can also look in Google Scholar for Fairnairn's publications. She wrote several papers on sexual size allometry, among which this one on Rensch's rule:

A Comparative Analysis of Allometry for Sexual Size Dimorphism: Assessing Rensch's Rule

Ehab Abouheif and Daphne J. Fairbairn

The American Naturalist , Vol. 149, No. 3 (Mar., 1997), pp. 540-562

Available here:

http://biology.mcgill.ca/faculty/abouheif/articles/Abouheif,%20Fairbairn%201997.pdf

Homo sapiens

Also some fresh water crustaceans have larger males- look at papers from Amir Sagi's group.

And how about cattle and buffaloes?. The males are much bigger and heavier than the females.

I think that in black-widow spiders, if the minuscule male is not escaping immediately after mating, the many times larger female simply devours him...

ta kind of buttefly Scarce Vapourer (Orgyia recens) The wingspan is 35 to 40 millimetres (1.4–1.6 in) for the males, the females are wingless. so is so smaller than without wings. also many birds the male is colorful and bigger than females like

Wild Duck (Anas platyrhynchos) and Common Pheasant (Phasianus colchicus)

Hy David I know some significat difference is size in some marine Mollusks. Two good examples are Lambis lambis (Linné, 1758), Cassis cornuta (Linné, 1758) and some more.

Gianluigi Bini

there is a significant different in size of sexes in order Cladocera both marine and fresh water species. females reproduce parthenogenetically in spring and summer and consequently new females are occured. when water temperature decreased females produce males which much smaller than females. So, males only occur in inappopriate conditions and outnumbered.

Some odontocete cetaceans. For example, in the sperm whale adult males weight about 40-50 tons while adult females only about 10-20 tons. Pilot whales (genus Globicephala) and killer whales (Orcinus orca) are also quite dimorphic.

In general, otariid pinniped males are larger than females. Among the phocid pinnipeds, male elephant seals (Mirounga) are much larger than females.

Elephant seals, with their harem mating system, are famous examples, quite well-studied. Males can be up to 10 times the weight of females, and reach sexual maturity at a higher age. Whereas females tend to reproduce first when about 3 to 5 years old, and then often give birth to a pup each consecutive year thereafter for may be 10, 15 years (the oldest known reproductively active females were >25 years old), males normally cannot do so until they are about 7 to 10 years old. Only the very biggest males will be able to maintain a 'harem' of females and so be able to successfully reproduce. It takes them that long to grow big enough to be able to do so. Although they may mate with hundreds of female seals in that one particular breeding season, males often die shortly after or the year after, may only have a 'secondary' position nearby a harem. Only very few males are able to maintain a harem 'beachmaster' position for a couple of years in a row. The different life-history strategies between males and females have led to the enormous sexual size dimorphism in elephant seals. Many other seal species are a bit like elephant seals (grey seals, for example), although less extreme. There are many fascinating papers about this, written between the late 1960s and the present.

Lamprologus callipterus males are apparently up to 60 times heavier than the females.

See: Kazutaka Ota, Masanori Kohda & Tetsu Sato (2010). "Unusual allometry for sexual size dimorphism in a cichlid where males are extremely larger than females". Journal of Biosciences 35 (2): 257–265. ( http://www.ias.ac.in/jbiosci/ota_380.pdf )

in accordance with dear Bensahla Lotfi

it's not bad to pointing some example of hermaphrodite species like Labridae and Scaridae(parrot fish) family .Almost all species are sequential hermaphrodites, starting as females (known as the initial phase) and then changing to males (the terminal phase). However, in many species, for example the stoplight parrotfish (Sparisoma viride), a number of individuals develop directly to males (i.e., they do not start as females). the protogynous female which changes to male sexually is the biggest one in the school and called the terminal male . these males vigorously defending their position from any challenge to the other initial males . the same sex changes is reported in some hermaphrodite species of Serranidae, too.

A classic example is the anglerfishes. Check that link and all te references on fishbase http://en.wikipedia.org/wiki/Anglerfish

I don't know of any plant examples but such variation in sexual size-dimorphism falls under what is called Rensch's rule. Daphne Fairbairn has a good review with several examples in Fairbairn. 1997. Allometry for sexual size dimorphism. Annual Review of Ecology and Systematics 28:659-687.

She says that although one can find female-larger and male-larger examples throughout many animal families, male-larger dimorphism is really only predominates in birds and mammals. She says this reaches its most extreme in Primates, Pinnipeds, Proboscidea, and Artiodactyla where males may be 2-8 times heavier than females. Although mostly about animals, she does mention that male-larger dimorphism may tend to be larger in polycarpic seed-bearing plants.

Fairbairn also has a book just published this year called "Odd couples: extraordinary differences between the sexes in the animal kingdom". I haven't seen it yet but suspect it will have lots of examples with really big size differences.

Mountain gorillas

Am fisheries specialist, from my experience on fishreproductive biology, most of the fish species around the Arabian Gulf showed size differences. the big size size tend to the female and this indicated by length-weight relationship where the b value more or less in female are higher than male. For those working on growth for separation sex, they also found that L infinity are higher in Female than male.

Size dimorphisms where males are bigger than females are common in mating systems with contest-based competition among males for access to females (polygnous mating systems, including lekking). This is the case for the mammal systems mentioned above (e.g. gorillas, sperm whales, pinnipeds, deer/antelopes etc). However, these may not qualify as the kinds of example you are looking for as none of these size dimorphisms are as extreme as those you see with small males in the systems you mention. This is because males do not really have a minimum size to be able to function effectively as males (by definition males can get away with contributing the bare minimum genetic material during reproduction), while females (by definition) still need to provide the basic resources required by a functioning zygote, even if they're subject to intra sexual selection (competition for mates). For more on these general issues, I recommend Chapter 7:

http://www.amazon.com/Introduction-Behavioural-Ecology-Nicholas-Davies/dp/1444339494/ref=sr_1_1?s=books&ie=UTF8&qid=1361457601&sr=1-1&keywords=behavioural+ecology

It is common amongst reptiles, particularly lizards. A good reference to start is the following which you can obtain as a pdf through Google :

The evolution of sexual size

dimorphism in reptiles

Robert M. Cox, Marguerite A. Butler, and Henry B. John-Alder

See the attached for more on the issues

Sperm whales and California sea lions would also be good examples among marine mammals.

David, perhaps kelp gametophytes along macroalgae have one of the most stiking difference between males and females.

The female betta fish are smaller, and duller than the typical male betta fish

Tropical squids of family loliginidae are a good example where females are much smaller than males (by factor of 1.5 to 2). Males grow at slower rate but reach larger sizes.

There is sexual dimorphism in Antarctic fur seals (Arctocephalus gazella). Full grown males (bulls) holding breeding territory are ~200 kg, whilst females are ~35-40 kg (see [i] Boyd, I.L., McCafferty, D.J., Reid, K., Taylor, R., Walker, T.R. (1998) Dispersal of male and female Antarctic fur seals. Canadian Journal of Fish and Aquatic Sciences. 55: 845-852; and [ii] Boyd, I.L., McCafferty, D.J., Walker, T.R. (1997) Variation in foraging effort by lactating Antarctic fur seals: response to simulated increased foraging costs. Behavioural Ecology and Sociobiology. 40: 135-144).

Southern elephant seals (as another contributor noted) also show considerable dimorphism with males weight 3000-4000 kg and females up to 1000 kg (see Boyd, I.L., Walker, T.R., Poncet, J. (1996) Status of Southern Elephant seals, Mirounga leonina at South Georgia. Antarctic Science. 8(3): 237-244>

Hello, Your question had been so open as you see in the previous answers. There are several invertebrates which show this characteristic. In some case is just some part of its morphology which is diferent as in Uca sp, where the male has a chelates, which is bigger than the other. This chelates us used to fight, defend the territory or a female against other male and, also to courtship to female.

as a general rule, mainly in marine organisms, females are bigger than males because they must spend much energy in reproduction than males. According to this most species which change sex during development (many sparids for example) first are males and after reach some critical size became females.

the exeception to this rule is when males play a critical role in reproduction process (further than contribute with sperm). For example deffending the eggs or a territory. In this cases (as in the mentioned by previous contributors competing for females) size is important to get the objective and males can be larger than females. This is the case of groupers among fishes and some gobids and blenids.

One example of sexual size dimorphism is the bat Myotis nigricans. In this species, females are substantially larger than males. They differ in body weight, skull measurement, and forearm length. The difference in size is believed to be caused by natural selection for a large female size due to a fecundity advantage. The interaction between the sexes and energetic needs such as time and energy required to produce viable offspring make it favorable for females to be larger in this species. Females bear the energetic cost of producing eggs which is much greater than that of the male who only bears the cost of making sperm.

Pinnipeds: Steller Sea Lions show a considerable difference in size between males and females.

In a few Cichlid species males are often slimmer, but larger than females, and are more vibrantly colored. The dorsal and anal fins of the male are more pointed, larger, and more flowing than the female.

In the Order Primates, the genus Gorilla has already been metioned, or inferred, a few times (Luis Tito de Morais, "chimps and gorillas"; Jeff Arendt, "Primates"; Shelby Temple, "Mountain gorillas"; and, Sasha Dall, "gorillas"). The largest extant primate species in Grauer's gorilla (Gorilla beringei graueri), but the greatest degree of sexual dimorphism among extant primate species is that exhibited by males and females of the two orangutan species: the Bornean orangutan (Pongo pygmaeus), and the Sumatran orangutan (P. abelii). Among the non-hominoid primates, the greatest sexual dimorphism would be that exhibited by the largest species of Old World monkeys, the mandrill (Mandrillus sphinx), and the drill (M. leucophaeus). Among fossil primate species, Lufengpithecus lufengensis (an extinct ape dating to the latest Miocene of southern China) exhibited greater sexual dimorphism than any extant primate -- so much so, that it was mis-classified as two species, a larger one (which turned out to be male L. lufengensis), and a smaller one (which were actually female L. lufengensis). Above, Tito also draws attention to the Reno et al (2003) paper, "Sexual dimorphism in Australopithecus afarensis was similar to that of modern humans." PNAS 100 (16) 9404-9409. Subsequent analyses of sexual dimorphism in Australopithecus afarensis compared to that of other hominoids has led to a revising of this interpretation. Gordon et al. (2008), in a paper entitled, "Strong Postcranial Size Dimorphism in Australopithecus afarensis: Results From Two New Resampling Methods for Multivariate Data Sets With Missing Data" (Am. J. Phys. Anthro. 135:311–328), indicate that their results show that A. afarensis exhibited post-cranial sexual dimorphism that was similar to what is seen in extant gorillas and orangutans (see attached). They infer this must have meant A. afarensis exhibited rather different mating strategies from Homo spaiens -- again, as has been pointed out above, the apparent strong postcranial sexual dimorphism of A. afarensis would suggest a high degree of male-male competition for mating opportunities with females.

Frogs exhibit sexual dimorphmism. An example of this are in tusked frogs where the male frogs are bigger and have bigger tusks for mating and rivalry compared to their female counterparts.

The female of a polar bear is relatively smaller than the male except during pregnancy period where females may be fattened up to aid the growth of cubs.

In case of low land mountain gorillas from the congo basin of africa also have smaller female and large male which is usefull to defend from predators and fellow competition. The same is true in case of baboon's .

There is an example with fish; Semicossyphus darwiini, it is a protandry species that goes from a small-juvenile female stage and develops into a large male. It is a common feature in wrasse fish.

In bullfrogs (Rana catesbeiana), adult males are larger than females, but this is the reverse of many species of anurans.

From Wikipedia: "For many frog species, the females are significantly larger than the males. This is to accommodate the amphibian mating process called amplexus. The male climbs on top of the female and she supports his weight as she discharges eggs and he spreads sperm on top of them." For a recent example of extreme sexual size dimorphism in frogs, see: Bishop P and Narins PM (2020) Call morphometrics and extreme sexual size dimorphism in the Fijian ground frog Cornufer vitianus (Anura Certatobatrachidae). Pacific Science, 74(1): 49-63. https://doi.org/10.2984/74.1.4.

The most extreme case I know of in amphibians is in the African Bullfrog (Pyxicephalus adspersus) @David J. Garbary where the males are much larger than the females (twice as heavy).

In the Dragonet (Callionymus lyra), a fish from the East Atlantic, the male gets much larger (30 cm) than the female (20 cm). Due to this difference, males and females were originally even described as two different species.

Dr. Bishop,

How does the male-to-female SVL ratio in Pyxicephalus compare to say, that of some the exceptional Pacific amphibians? For example, I recently read that Cornufer boulengeri in the Bismarck Archipelago, Papua New Guinea, represented the most extreme known example of sexual size dimorphism among frogs with a male-to-female SVL ratio of 3.10.

Thank you for your help,

Peter Narins

New estimates indicate that males are not larger than females in most mammal species

https://www.nature.com/articles/s41467-024-45739-5