True/False? Investigating a few questions around hyenas.

Kweli/Uongo? Uchunguzi wa maswala kuhusu fisi.

Hyenas are dogs. True/False FALSE

There’s an age-long debate I hear about whether hyenas are dogs or cats. They do look a bit more like dogs but they are actually in their own family called the Hyena family. The hyena family is in a big group of carnivores called the Feliformes. The other big group is the Caniformes and that’s where dogs are, so hyenas are more closely related to cats than dogs. But that’s not the full story. Hyenas are actually more closely related to the mongoose family, and then to civets and genets than they are to cats. Here’s what the family tree looks like:

The family tree drawn to show the relationship of hyenas to the other members of Carnivora. Hyenas and mongooses are the most closely related as you can see by the red branch. Their next closest relatives are the civets and then the cats. Dogs are off on a completely different branch.
Adapted from Jonathan Kingdon, Mammals of Africa, Vol V. pg 24. & pg 24 of Victor Vinuesa’s dissertation.

Fisi ni mbwa. Kweli/Uongo UONGO

Kuna mjadala wa siku nyingi unaojadili kama fisi ni mbwa au paka. Kwa kweli, fisi wanaonekana kama mbwa lakini wako kwenye familia yao peke- familia ya fisi (Hyenidae). Familia ya fisi iko kwenye kundi kubwa ya Carnivora linaloitwa ‘Feliformes’. Kundi kubwa nyingine ni ‘Caniformes’ na mbwa wapo kwenye hiyo. Hii inamanisha kuwa fisi wako karibu ziadi na paka kuliko mbwa. Likini hii sio mwisho wa maongezi yetu. Kwa kweli, fisi wako karibu zaidi na familia ya vicheche, nguchiro na fungo, kuliko paka. Chati hapo juu inaonyesha uhusiano wao.

Hyenas are mainly scavengers. True/False FALSE

Hyenas are efficient scavengers and can smell carcasses a few kilometers away. They can steal kills from cheetahs, leopards, and even lions, a behavior called kleptoparasitism, but they actually hunt most of their prey. Hyenas kill between 60-90% of the animals that they eat.

Fisi ni mwokotezaji. Kweli/Uongo UONGO

Fisi ni mwokotezaji hodari sana na anauwezo wa kunusa mzoga wa mnyama kwa umbali wa zaidi ya kilometa mbili. Wanaiba mizoga ya duma, chui na hata simba, tabia linaloitwa ‘kleptoparasitism’, lakini ukweli ni kwamba wanawinda sehemu kubwa ya chakula chao. Fisi huua asilimia 60-90% ya wanyama wanaowala.

Hyenas are hemaphrodites. True/False FALSE

Probably the most peculiar thing about spotted hyena is that females are larger than males and have a fake penis and fake scrotum. Scientists call it a pseudopenis but it is actually just the modified female anatomy. It is interesting that scientists still don’t really know why. The feature actually has a huge cost. The pseudopenis is also the birth canal and in 1st time mothers is so tight that more than half of females’ 1st cubs usually die giving birth. 1-2 out of 10 females die giving birth, too. So why would they have developed this?

Hyenas are such efficient killers and meat eaters that when they make a kill the competition is intense. Bigger more aggressive hyenas get more meat which means their chances of survival and raising their cubs is higher. Researchers suggest that this is why females are bigger than males.

Hyenas are also exposed to a higher level of “male” hormones when they are still in the uterus, and for a long time scientists thought that that was why females developed the male-like genital organs. However, it turns out that the development of the external genitalia of the female happens before the development of the ovaries, which means it is happening before hormones are influencing the development. They also tested this by giving pregnant female hyenas hormone inhibitors and the female hyenas still developed their normal organs. The interesting thing is that male hyenas born from mothers that had been given the hormone inhibitors developed the female like pseudopenis.

One theory suggests that because females have to invert the pseudopenis in order to mate, she has total control over which males she allows to mate, but female hyenas are dominant over males who are submissive anyway.

There are a number of other theories but none of them have enough evidence so in my opinion, it’s best to appreciate that there are still some big mysteries in the natural world.

Here is a cool short video that explains it too. It’s only 3 minutes.

Watch more about hyena social structure here. Angalia zaidi husu fisi- bonyeza hapa.

Fisi ni huntha (‘hermaphrodite’). Kweli/Uongo UONGO

Labda kitu cha kushangaza zaidi kuhusu fisi ni kwamba jike huwa mkubwa kuliko dume na ana viungo vya uzazi bandia vya dume – mbo na uke. Wanasayansi waviita ‘pseudopenis’, lakini ukweli ni kwamba ni viungo vya uzazi vya kike vilivyobadilika kipekee. Sababu yake haijulikani na wanasayansi. Badiliko hii ya kiumbili inamgharimia sana.  ‘Pseudopenis’ ni njia ya kuzaa na huwa asilimia 60% ya watoto wa kwanza wananyongwa wanapozaliwa. Vilevile, jike mmoja hadi mbili kati ya majike kumi huufa pia wakati wakuzaa kwa mara ya kwanza. Ni kwa nini basi?

Fisi ni muaji na mlanyama fanisi hadi wakiwepo kwenye mauaji na mzoga, huwa upinzani unakua mkubwa sana. Fisi wakubwa na wenye hasira zaidi wanapata nyama zaidi, na kuongeza uwezo wa kuishi na kulea watoto. Watafiti wanadai kwamba hii ndiyo sababu ya majike kuwa wakubwa kuliko madume.

Fisi mtoto akiwa tumboni hupata kuonyeshwa kiasi cha hormoni za ‘kidume’ akiwa bado hajazaliwa, na kwa muda mrefu wanasayansi walihisi kuwa ndiyo sababu ya majike kubadilika kuwa na viungo vya uzazi vinavyofanana na za dume. Lakini, walivyochunguza zaidi, inaonekana kwamba kwa fisi mtoto dume akiwa tumboni viungo vya jike vya nje hujitokeza kabla ya ovari kujitokeza, na hiyo inamaanisha inatokea kabla ya hormoni kuwa na matokeo. Walipima nadharia hii kwa kuwapa fisi majike wazazi madawa ya kuzuia hormoni za watoto jike kabla haijajitokezea na ‘pseudopenis’. Cha kushangaza zaidi, madume waliozaliwa kwa hawa mama waliopewa dawa hizo za kuzuia hormoni, wajilitokeza na viumbe vya uzazi vilivyo fanana na majike. 

Nadharia nyingine inadai ya kwamba ni njia mmoja wapo ya majike kuhakikisha asipandwe na dume yoyote. Ili kupandana, inabidi jike aikunjie ‘pseudopenis’ yake ndani ilikukumruhusu dume kupanda na hiyo inampa nguvu ya kumtawala dume. Tatizo la nadharia hii ni kwamba dume huwa anatawaliwa na jike.

Kuna nadharia nyingine nyingi pia lakini hazina ushahidi wa kutosha, na kwa maoni yangu bora tupendezwa na maajabu mengine yasioeleweka bado.

Hapa juu kuna tuvuti nzuri inayoelezea hayo au bonyeza hapa.

Sources:

Kingdon, Jonathan & Hoffmann, Michael. 2013. Mammals of Africa, Volume V, Carnivores, Pangolins, Equids & Rhinoceros. Bloomsbury.

Smith, Jennifer & Holekamp, Kay. 2018. Spotted Hyenas. Elsevier.

Vinuesa, Victor. 2018 Bone Cracking Hyenas from European Neogene & Quaternary: Taxonomy, Paleobiology & Evolution. Universitat Autonoma de Barcelona.

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