Cage size vs declanning, and declanning causes

[Markpd]

Early on when I began to read up about Gerbils nearly a year ago (after not having gerbils for a very long time), I occasionally came across the 'rule' of a maximum cage size for gerbils (10 US gallons/gerbil), which if exceeded could allegedly cause declanning. The idea that large tanks can cause de-clanning I found baffling (and is what set me off onto my investigation), primarily because on the face of it, it doesn't make sense due to the fact that in the wild they (effectively) have infinite space, and far more space than any cage we could (likely) realistically provide!

I'd like to point out straight up that I haven't found all the info I would like and so this post isn't finished, mainly because the info doesn't exist or is scattered over the web or forums amongst hundreds (maybe 1000s??) of threads for well over a decade! I'm mainly thinking declanning rates there, it would be very useful to show for example that the declanning rate in Germany (where lots of forum members have large 100cm+ cages) is no higher than it is here in the UK or US. But a database of declanning rates doesn't exist here or in Germany AFAIK.

I have created a thread asking just that question in this forum (here - gerbilforum.proboards.com/threads/recent/34726 ), and I will be linking to it from the German forum and maybe Facebook groups too, but it's early days and we only have about 20 experiences so far. Feel free to add to it if you haven't already!

There are also some more papers I'd like to read, e.g "Social factors affecting litters in families of Mongolian gerbils,Meriones unguiculatus" Elke SCHEIBLER*, René WEINANDY and Rolf GATTERMANN 2005, and (read again properly) "Inter-group associations in Mongolian gerbils: Quantitative evidence from social network analysis" by Wang et al 2017 and "Relatedness and spatial distance modulate intergroupinteractions: experimental evidence from a social rodent" 2018 by Ke DENGa,b, Wei LIUa,c*, De-Hua WANGa,(very interesting papers about how different neighbouring groups get on. Spoiler! They aren't always hostile to each other! ).

The TLDR (short version).

I've not found any research papers to date that back up the theory that large cages can cause declanns.

So far, the few sites/people I've found that promote the large cage causes declanning theory haven't provided any links to research supporting their claim, nor good explanations of their declanning incident(s) (where any).

Their are multiple reasons that can cause declanning, sometimes more than 1 at a time, it can be very hard or impossible sometimes to know which cause, or causes it was.

In the wild, groups of gerbils live in burrows/territory which are at least a few 100 metres squared.

Mostly, it is only the breeding pair that are the 'stable clan' of the group, except through the winter where the latest litter will remain until the spring.

Gerbils rarely live more than a year old in the wild.

For more details, read on!

Territory sizes and roaming ranges.

In the wild, clans of gerbils have been found with very large territories - "The territory belonging to each group ranged from 325 to 1550m2 depending on group size, food availability and most importantly the body weight of the largest male gerbil.", according to the 1989 research paper by Agren et al (pay walled, £40 , published in the journal Animal Behaviour) . See a free exert here - s469337723.websitehome.co.uk/gerbils/wild.htm

The 2011 paper Home-range sizes of social groups of Mongolian gerbils Meriones unguiculatus by Wang et al found "Average monthly home-range sizes of social groups were 309.10 m2 +/-50.97 (n=42) during the breeding period and 262.5 m2 +/-103.6 (n=9) during the non-breeding period".

And the book 'Rodents in Desert Environments' edited by I. PRAKASH & P. K. GHOSH, 1975, relates to other articles discussing some more exceptional individual gerbils as well as more typical gerbils. "Their daily run in summer is of the order of 1.2 to 1.8 km (BANNIKOV, 1954). One marked animal moved over a distance of 50 km[!]. Movements over distances of 15 to 20 km from their home burrows have been recorded (NEKIPELOV, 1959)", exert from the book from this site.

Group sizes

In the wild, for the most part, the only 'permanent' clan members are the main breeding pair - "Groups consisted of up to 17 individuals. A typical group had an adult male and an adult female living with up to 3 litters of offspring" Argen at al 1989. (though they aren't always monogamous**). So the 1st litter helps out with the care of the 2nd litter* etc, but not breeding themselves, and any remaining litter(s?) also helps with hoarding in the autumn, helping survival through the winter. Come the spring, the last litter leaves.

*Where there is one, in the 2009 research paper Population Ecology of Wild Mongolian Gerbils by Liu and Wang et al, they found "April through late August in 2006. Forty-one (23.4%) of 175 captured females reproduced during the breeding season. Of these, 80.5% (33/41) bred once, 7.3% (3/41) bred twice, and 12.2% (5/41) bred 3 times.". "We had 2,544 captures of 340 individual (165 males and 175 females) gerbils from April through October 2006. We observed 164 social groups and 46 solitary individuals during our 12 trapping weeks at 30 burrow systems. Social groups consisted of 2–18 individuals."

Also the above paper refers to an earlier paper by E.Scheibler  "Behavioral observations suggest that Mongolian gerbils are socially monogamous: male and female founders form a pair until 1 of them dies or disperses (Scheibler et al. 2004)."

It's worth noting Gerbils in the wild often don't live to be even a year old! , Argen et al 1989 "Of the 126 gerbils caught 19% were juveniles, 54% subadults and 27% adults. Only 4% of the adults were likely to be aged at least 8 months old."[!]

** "However, some gerbil communal groups had >1 breeding female; this finding is contrary to previous findings from laboratory studies that gerbils were socially monogamous and only founding pairs bred in social groups (Clark and Galef 2001). Agren et al. (1989a) also reported extrapair copulations in wild Mongolian gerbils." Again from the 2009 paper by Liu and Wang et al.

Declanning and max cage size theory

I have no experience of de-clanning myself (as of this posting, the current pair I have I got on August 2nd 2020, prior to that it was 32yrs! lol), but looking at the research papers that I can read (those which aren't behind a paywall!), animal charity/rescue centre sites, breeders sites, notes/observations from experienced Gerbil breeders and owners here and elsewhere, it seems to me (so far) that overall their is no real evidence of the max size rule, e.g I haven't yet come across any research papers stating it or equivalent in the wild. I have found a few indirectly contesting it though.

I have found a breeder in Austria who states that going over 150cm (~5ft) long cage can cause problems, even if this is true, it is far bigger than the 10gallon/gerbil 'rule'. The typical 150x60x60cm tank is 143 US gallons! As far as I've found to date, I've not seen anyone else state this large maximum size recommendation. She also states here (translated) that " It doesn't matter how big the enclosure is, as this was unfortunately often spread.", so contradicting herself. I've emailed (5/5/21) her to see if this can be cleared up. 

Their is a breeder here (who was active until ~2yrs ago) who vigorously supported the 10gall/gerbil idea, but in the posts I've seen she's citied no papers (stating the ones she had saved were lost on an old PC), and their is key information missing in her early declanning experiences. I will be asking her questions to see if I can find out more, but last I looked she hadn't logged onto this forum in over a year.

The take home point at this stage, is that their seems to be very little support for the max 10gall/gerbil rule.

Declanning causes

Declanning can have many causes, I will list some here, but it is not an exhaustive list, if anyone sees one or some missing, let me know and I'll add it . Also it would be interesting to see peoples experiences with the reasons I do have listed, so as to add detail.

Common declanning reasons/risks (so that doesn't mean they will declann for certain under such scenarios):-

Change of bedding (especially if none of the old bedding was kept), so a loss of group scent causing them not to properly recognise each other.

A section of the cage that is easily defended and blocked off by 1 gerbil (e.g 1 small entrance/ramp/stairs etc).

Multiple linked cages, even with multiple entrances (they could easily setup largely isolated separate homes/territories)

Illness of the dominant gerbil (making him/her weaker, and so can be challenged by the other gerbil(s)).

Being separated for too long (I believe this to be in the range of a few hours or more, but I would like feedback on this especially), e.g a vet visit with a gerbil separate from it's cage mates.

Some scent outside the cage over powering/interfering with the scent in the cage. e.g strong air fresheners.

A sudden and large increase in cage size (even when the old bedding is transferred), this issue is well known in the German forum (rennmause.de), and it is recommended there that when giving gerbils a much larger cage, to initially not allow them to have the whole cage area, but section it off and open it up gradually over a period of weeks (I'm afraid I don't know the details of the timing still, something I need to look more into). Btw, this particular issue is what I think could have largely given rise to the theory that large cages supposedly can cause declanns.

2 gerbils just don't get on! (ever or anymore).

Gerbils not being related

Unrelated gerbils being introduced after the pup stage.
Groups of 3 females or more (even if related, but they are at a lower risk than unrelated ones).

Groups of 3 males or more (as long as they are siblings, the risk is much lower than with females).

Rare(?)/oddball reasons:-

1 gerbil being unsettled by the other gerbil being handled, even when they are both being handled! (Yes seriously! Lol betty had this issue, although she spotted this before any possible declan happened).

1 gerbil being particular obsessed/possessive over a particular item.

Too small a cage (even if when above the minimum), lilyanddaisy had this occur with a female & neutered male pair where they were tense & constantly bickering, moving them from a 75cm to 120cm long tank instantly improved their behaviour. (Not sure if this one is rare, but I've only occasionally heard of this so far, that I recall!)

One method of avoiding an impending declan is to temporarily use a smaller cage (or reduce the size of their current cage). This method might be another point where the idea of a max (small) cage size comes from, which might sound contradictory to what I've said above, but where the de-clan was caused by a transient problem, removing their normal 'toys' and forcing them to be closer together encourages them to interact more, if they get on better again, then after a few months or so they can have their cage gradually opened up again or returned to the bigger cage. If they still don't get on, or go to a full declann, then it may simply be that those gerbils just don't get on with each other.
But at the end of the day, it's not the best for the gerbils to force them to stay in a bare minimum cage on a permanent basis just to try to keep them living together.

Cage size, supporters of the 'bigger is better' idea

I have found these organisations/institutions that support the idea that 'bigger is always better' and no max size cage rule.

The Veterinary Association for Animal Welfare (TVT, Germany) 100x50x50 for a pair, plus a 30cm topper.

The Swiss Animal Welfare "....the minimum would be a terrarium of 140x60x60 cm [~4.6' x 2' x 2'] for 2-4 animals, but bigger is always better. That in larger terrariums it can cause sudden aggression is not proven".
The following rescue centres/charities in the UK (although all these have lower min's than above, they support bigger is better) :-
RSPCA, Bluecross, Raystede, Pets corner, Woodgreen animal ctr, Gerbil and Rodent Rescue UK.

And from this forum, at least a few breeders too, who I won't name in case they want to stay out of this discussion.

Gerbil breeders USA
Wild prairie - wildprairiegerbils.weebly.com/gerbil-care-basics.html
Moonstone Gerbils (via email, not on website, "The amount of space they get doesnt really effect how likely they declan.").
Kelly Roper - small-pets.lovetoknow.com/rodents/how-care-pet-gerbils

Please let me know if you come across other breeders, charities or rescue ctrs that explicitly state that bigger is better, or at least large cage sizes (any country).

Cage stats/info

Some cage size recommendations/min requirements :-
Germany - Min rec. 100x50x50cm (2-6 Gerbils) .......................... (250 lts, 55 imp gall, 66 US gall, 5000 cm2)
Austria - Min req. 80x50x50cm ................................................... (200 lts, 44 imp gall, 53 US gall, 4000 cm2)
Swiss - Min req. 100x50x30 (2-5 Gerbils) ................................... (150 lts, 33 imp gall, 40 US gall, 5000 cm2)
Swiss - rec 120x60x60 ............................................................... (432 lts, 95 imp gall, 114 US gall, 7200 cm2)
Swiss Animal Protection - min rec. 140x60x60[!] (2-6 Gerbils) ... (504 lts, 111 imp gall, 133 US gall, 8400 cm2)

Random related info/notes

A few notes I made about some of the German and Austrian website authors.
Rennmause Info, general research from papers and books, Christine Wilde possibly qualified in behavioural research, (self taught initially) - www.diebrain.de/re-gehege.html#gross , min advised size 120x60x60cm (bigger is better).
Castle mouse - Tinka Joselin Müller, Gerbil breeder since 2008 - www.schlossmaus-zucht.de/ and www.schlossmaus.de/ , min advised size 120x60x60 cm for 2 Gerbils (min 20cm bedding), bigger is better.
Nagerbau (long term rodent owner, self taught) - nagerbau.de/rennmaus/rennmaus-gehege/ , 100x50x50 min, 120x60x60+ advised.

Maustria - Sabrina, kept Gerbils since 2008, also breeds them (unknown how long), rescue ctr (foster home), offers intro'ing gerbils as a service, max cage length 150cm and no max size! [site has contradictory info, emailed her 5/5/21] www.maustria.at/

Also, and I appreciate this isn't solid info, but in Germany, and in their rennmaus.de forum it is widespread good practice there to consider a minimum cage size as 100x50x50cm (66 US gallons, 55 imp gallons, 250 lts), with a decent size being 140cm and upwards! An English lady recently posted about her cage (and Gerbil colours) there www.rennmaus.de/community/thema/173485-haltung-in-england-abgetrennt-aus-farbfrage/?pageNo=1 , with people noting that the cage is only 60x30cm (~2'x1') floor area (1800 cm2), people were wondering if it was just a transport cage! When they found out it wasn't, they seemed genuinely shocked that she had such a small cage for them! She was getting quite a bit of heat about it (although as far as I could tell it was polite). Bear in mind, that like here, some of their members at least will be breeders and experienced owners, not just hardcore animal welfare advocates.

(Btw, in case you use Google translate for German rodent sites, haltung does NOT mean attitude in the context it is used there, more like housing and care, just to avoid crossed wires! Google gets that wrong!).

Some more info/links.

Re declanning - Intra-family aggression and offspring expulsion in Mongolian gerbils (Meriones unguiculatus) under restricted environments by Elke Scheibler, R. Weinandy & R. Gattermann 2005 (pay walled, £30 ) link.springer.com/article/10.1016/j.mambio.2004.12.002
Social categories in families of Mongolian gerbils by Elke Scheibler, R. Weinandy & R. Gattermann 2004 (pay walled, £40 ) - www.sciencedirect.com/science/article/abs/pii/S0031938404000551?via%3Dihub

Social factors affecting litters in families of Mongolian gerbils by Elke Scheibler, R. Weinandy & R. Gattermann 2005 (free! ) - www.researchgate.net/profile/Elke-Scheibler/publication/228514938_Social_factors_affecting_litters_in_families_of_Mongolian_gerbils_Meriones_unguiculatus/links/0a85e53bf7ac0ea6f5000000/Social-factors-affecting-litters-in-families-of-Mongolian-gerbils-Meriones-unguiculatus.pdf

[LilyandDaisy]

Thanks for this! There's a lot of information here to digest.

I think you must have been thinking of someone else with the thing about handling. I don't remember having an issue like that, unless I'm forgetting something.

I do have something to add though. When I had Rocket and Storm in a 75cm tank they were so tense, constantly bickering and at one point sleeping separately. They literally changed overnight when I moved them to their current 120cm tank. They still argue from time to time, but much less often. So I think small tanks can potentially cause issues for some gerbils too.

[yeti218]

Ahhh, the much anticipated research we’ve been hearing so much about. Thanks for posting, very informative. Now if you’ll excuse me, off to buy a bigger cage....

[Markpd]

Lol, yea nearly 1yr after I started researching it (on and off), I finally posted it!

Lilydanddaisy
No probs , ah funny you say that, betty PMed me earlier with a nearly identical story, I guess it was her not you! lol
I'll add your experience to the list (and interesting btw), thanks

[LilyandDaisy]

Thank you, but you said a female pair in the article. Rocket and Storm are female and neutered male.

[Markpd]

Doh! That's my memory for you!

***********

 Have edited and added to the op.

[betty]

Yes, it was me confuzling things!

My females were so odd about that handling thing - or in the run. They never did declan though. She just used to totally beat her sister up each time she knew the sister had left the enclosure. I ended up not ever letting her know her sister had been out and the beatings stopped. Weirdos.

They lived very long lives together, my little angels...

[Markpd]

Lol, she was quite mean to her sister then!

[Markpd]

Bump for new members