Sudden bullying in a herd

[Cryptikality]

Hello, looking to find some advice on a recent development in our herd. We have one male and three spayed females, all between 2-3 years old that have been together for their entire lives.

Habitat:
We have a two story C&C cage with a large ramp, roughly 12sq ft for the first floor and 4sq ft for the second floor, with fleece liners and various hideys.

Herd: They have all been these weights (give or take 50g) since becoming full grown, we weigh them weekly. We're not really sure why one female has always been so much smaller than the others, but they did come from separate litters. They all seem perfectly healthy as far as we can tell (no rashes or hair loss, eating and going to the bathroom normally) They have always gotten along well, although they have never been snuggly to any degree with each other, all always like to lay by themselves.
Pebbles - Male, 1400g, 2.5yr
Willow - Female, 1200g, 2yr, spayed
Cleo - Female, 1200g, 2yr, spayed
Panda - Female, 800g, 2.5yr, spayed

About a week ago, the two larger females have started bullying Panda...nipping at her until she moves, or cornering her in a hidey until she starts wheeking loudly in complaint, at which point the male will go over and enforce the peace. We are consistently checking her afterwards, and there do not appear to be any bite marks or scratches on the skin, nose, or ears. However it keeps happening a few times a day, and has never happened before. She is still coming out for meals and eating hay and drinking, but we're deeply concerned by how frequent this behavior is and how upset she seems.

Any advice, thoughts, or comments would be much appreciated!

 

[Piggies&buns]

Welcome to the forum

Have you had them for all their lives?

The first thing to note is that upper levels of cages do not count towards the cage size. It is only the bottom level which counts and therefore needs to meet size requirements. Consequently your cage is not 16 square feet, it is only 12 square feet which is not really big enough for four piggies. It is only really considered big enough for three piggies.
So, space may be one issue.

You also mention cornering in a hidey - do your hides all have two doors in them? If not, then that is another potential issue. All hides should have two doors so that cornering cannot occur.

Do you have multiple of everything in the cage ie four bottles, at least four hides, four hay piles etc?

Nipping is a gesture of power. Her squeaking loudly is submission. She is telling them she isn’t a threat to them.
Neither of these things on their own are concerning - it is normal dominance and she is giving the correct response.
Bullying is a sustained behaviour which will often see the underpig lose weight, be chased away from food, not want to come out etc. Although sows can be a bit more underhand about bullying so it can sometimes be a bit harder to tell.
However, as it is a new development, I wonder if there has been any changes recently? Something to upset or shift the hierarchy in some way?

Ive added some guides in below which may be of help

Moody Guinea Pigs: Depression, Bullying, Aggression, Stress, Fear and Antisocial Behaviour
Sows: Behaviour and female health problems (including ovarian cysts)
A - Z of Guinea Pig Behaviours
Bonds In Trouble
Cage Size Guide

 

[Cryptikality]

Hi, thanks for your response!

Yes we have had them for all their lives. We do normally use some one-entrance hideys that they have always been fine with, but currently everything in the cage is two-entrance to help with the issue.

Nothing has changed that we are aware of, that's why we are so concerned. They have been together for two years and never exhibited this behavior before, and now suddenly its happening several times a day for about a week so far. We had never even heard Panda be this loud before, she's always been very quiet.