What is the capacity of a rhino’s bladder?
January 20, 2011 3:42 PM   Subscribe

What is the capacity of a rhino’s bladder?

I spied a rhinocerous having a pee recently and my son and I were astounded at how long it went on. (pic)

However extensive searching has failed to answer this question! Surely someone has thought to measure this at some stage.
posted by gomichild to Pets & Animals (15 answers total) 53 users marked this as a favorite
I bet these folks might know: http://www.rhinoresourcecenter.com/forums/
posted by misterbrandt at 4:07 PM on January 20, 2011

From Metabolism and excretion of oestradiol-17b and progesterone in the Sumatran rhinoceros (Table 1, p. 163), urine excreted per day:

Day 1: 15.4 litres
Day 2: 18.7 litres
Day 3: 28.4 litres
Day 4: 15.0 litres
posted by Paragon at 4:13 PM on January 20, 2011 [8 favorites]

Now we just have to determine how many times the rhino took the piss to make a guess at the bladder capacity...

Also: Christ.
posted by disillusioned at 4:18 PM on January 20, 2011 [3 favorites]

Response by poster: OK so know we need to know how many times a day they pee and at what percentage of the capacity they pee at.
posted by gomichild at 4:18 PM on January 20, 2011

That appears to be a white rhino in your photo. This 1990 study [pdf] collected all the urine (and feces) produced by a female white rhino over a four day period to measure hormone absorption. Table 1 on page 575 says that on day two of the test, 20 liters of urine was collected and on day four, ~21 liters of urine were collected. While that's not maximum capacity (like how much the rhino's bladder could hold if the rhino really had to go but there were no stalls available at the ballpark or something) but it's a good start.

On preview: it's interesting how the smaller Sumatran rhino can hold in more than a white.
posted by jamaro at 4:19 PM on January 20, 2011 [2 favorites]

OK so know we need to know how many times a day they pee

Much like the household dog, male white rhinos scent mark their territory by deliberately dragging their feet through their urine puddles as well as spray marking trees/bushes thus frequency isn't necessarily related to need-to-go. Dunno about the girl white rhinos.
posted by jamaro at 4:45 PM on January 20, 2011

Still with female Sumatran rhinos, from Endocrine and ultrasonographic characterization of a successful pregnancy in a Sumatran Rhinoceros (Dicerorhinus sumatrensis) supplemented with a synthetic progestin (Roth, Bateman, Kroll, Steinetz, & Reinhart, 2004):
During the 6 weeks of observation prior to labor, the female rhinoceros reportedly squirted urine a couple of times, and usually urinated in a downward style three or four times in each 12-hour period.
So, very very roughly, if a female Sumatran rhino urinates an average of 7 times per 24 hours, at an average volume of 19.4 litres (and assuming that they urinate when their bladder is full): about 2.8 litres?

There's too many variables for this to anything but a wild guess, though. And I hope I don't get into trouble for Googling 'rhinoceros micturition' at work.
posted by Paragon at 5:05 PM on January 20, 2011 [6 favorites]

Hmm... on further reflection, we can't really assume that animals urinate when their bladder is full. In humans, for example, the reflex to pee starts long before the bladder is at capacity.

I don't know enough about comparative anatomy to determine whether this approach would work: humans produce 1-2 litres per day, based on a bladder around 500mL in volume, so a human produces 2-4 times as much urine per day as their bladder capacity. Assuming the same ratio for a rhino gives the figure of between 4.8 and 9.7 litres.
posted by Paragon at 5:29 PM on January 20, 2011

Response by poster: I apologize in advance for any issues and associations with rhino porn while trying to find answers.

I guess I assumed that in some 18th century curio collection somewhere there would be a rhino bladder and someone would have measured it. Or possibly turned it into a hip flask.

So far I think we are getting a rough idea though so thanks!
posted by gomichild at 5:32 PM on January 20, 2011 [1 favorite]

During a 2nd grade school trip to the zoo my classmates and I witnessed the glorious spectacle of a female elephant, some fifteen feet in front of us, cock a vast hind leg exactly in our direction and, from betwixt pendulous vulvae, gush forth a raging, foamy cataract of amazingly luminous yellow piss.

The violence of the torrent was enough to crater the dirt beneath, and the volume was enough to fill a modestly-sized jacuzzi.

An elephant is surely highly comparable to a rhinoceros, so I'm sure that this tale, which I have carried in troubled silence all these long years, will be of use.
posted by Kandarp Von Bontee at 5:35 PM on January 20, 2011 [97 favorites]

I think if we're going to go with comparative anatomy we should look at horses.

Wikipedia lists horse weight as approximately 400 to 1200 kg, depending on the type. Rhinos go from 800 to 3800 kg according to Wikipedia, but if we consider your rhino a white rhino (I think it is because of the lip shape) we can narrow the weight range down to 1,300 to 3600 kg.

A normal equine bladder has a volume of approximately 4.5 L and a horse will produce 3 to 15 L of urine per day(about 5-15 mL per kg per day). The upper range of horse urine production seems to be about the mean daily urine volume produced by a rhino according to what has been posted previously. And an average urine production rate of ~9 mL per kg per day works out to about 20 L per day on a 2450 kg rhino which is in agreement with previous posts.

(Horse Weight)/(Horse bladder capacity)=(White rhino weight)/(White rhino bladder capacity)

(~1000 kg)/(~4.5L)=(~2450 kg)/(White rhino bladder capacity)

White rhino bladder capacity = ~11 L
posted by Lord Force Crater at 7:25 PM on January 20, 2011 [5 favorites]

I assume that animals usually pee far before they've pushed up against their capacity, so a more precise question is how much does a rhino typically expel each time it urinates. Elephant and blue whale estimates would be interesting too.
posted by dgaicun at 9:58 PM on January 20, 2011

I don't know. But here's a sketch (NSFW if your office minds rhino reproductive anatomy). It's from The Journal of Zoo and Wildlife Medicine.

Full citation: Journal of Zoo and Wildlife Medicine 32(1):31-46. 2001
doi: 10.1638/1042-7260(2001)032[0031:CIORRT]2.0.CO;2


Nan E. SchafferD.V.M., M.S.1, George L. FoleyD.V.M., Ph.D.1, Sophia GillD.V.M.1, and C. Earl PopePh.D.1

Maybe you could contact one or more of the authors--you can email Dr. Schaffer here-- and I can stop Googling for "rhino pee"?
posted by MonkeyToes at 4:00 AM on January 21, 2011 [2 favorites]

Once properly measured, I propose the rhinobladder to be Metafilter's new standard for liquid volume.

For example the homebrew article would call for 3 rhinobladders of Joe's Ancient Orange.

I also considered the rhinopiss, the rhinopee, the deluge d' rhino, and the OMG-what-do-those-things-drink.
posted by Abehammerb Lincoln at 12:00 PM on January 21, 2011 [2 favorites]

Are those bladder capacities measured on a dissected organ?

No, both studies were done on live rhinos, as explained the linked studies: "Reproductive monitoring of exotic animal species is best accomplished by measuring oestrogen and progesterone metabolites in urine and faeces collected non-invasively..."

From both studies, which had one researcher in common: "Urine was collected in [a
receptacle] beneath the external outlet of the enclosure drain."
posted by jamaro at 12:48 PM on January 21, 2011

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