Why is one of my guinea pigs suddenly bullying the other one?

[TMan4563]

I am a bit concerned because for the past few weeks one of my guinea pigs has suddenly started aggressively chasing one of my other piggies. I had 3 guinea pigs for about 2/3 years, and I recently introduced a new one that was about 6/7m old. This introduction was about 2 months ago, and she fit in perfectly fine with the rest of the girls. She was very timid and left everyone alone, and no one bothered her either. However, about 2 weeks ago I had to quarantine my alpha piggy for an illness, and the problem piggy started this behavior. I asked my vet if I could treat all of them and put the alpha back in the cage to avoid the fighting, and this is what I wound up doing. However, ever since then the new girl has continuously chased and bullied one of the others. The girl being bullied does not fight back and just runs away and cries, and I am concerned about why this behavior suddenly arose. It is getting to the point where it is consistent enough that I am getting irritated because she is relentlessly bullying her. Is this normal? Is this temporary? Why did it only now occur when they were fine for a while?

P.S. They are all female and live in a 2x8 C&C cage

 

[Piggies&buns]

You ask why now - a medical separation has the potential to cause bond problems which is why they are not recommended.
You say you had to quarantine but then put them back together - a couple of questions:
how long were they apart ?
how long have they been back together?

Where in the hierarchy is everybody?
You say it was the dominant who had to be removed. This could have caused the next in line to try to take over, and then subsequent piggies down the line. Has the dominant regained her position as dominant upon reintroduction?

The crying you report may just be submission which is perfectly normal. You dont necessarily want her to fight back - if she does that then it could be a disaster anyway.
Dominance is one thing but there is a fine line into bullying which is a sustained behaviour. You might see the bullied piggy lose weight through never being allowed to eat and become withdrawn.

Use this guide below to help you establish whether what you are seeing is them in a normal period of reestablishing following a separation or whether there are deeper problems in their bond which may mean they cannot continue to live together.
Bonds In Trouble

 

[TMan4563]

You ask why now - a medical separation has the potential to cause bond problems which is why they are not recommended.
You say you had to quarantine but then put them back together - a couple of questions:
how long were they apart ?
how long have they been back together?

Where in the hierarchy is everybody?
You say it was the dominant who had to be removed. This could have caused the next in line to try to take over, and then subsequent piggies down the line. Has the dominant regained her position as dominant upon reintroduction?

The crying you report may just be submission which is perfectly normal. You dont necessarily want her to fight back - if she does that then it could be a disaster anyway.
Dominance is one thing but there is a fine line into bullying which is a sustained behaviour. You might see the bullied piggy lose weight through never being allowed to eat and become withdrawn.

Use this guide below to help you establish whether what you are seeing is them in a normal period of reestablishing following a separation or whether there are deeper problems in their bond which may mean they cannot continue to live together.
Bonds In Trouble

Thank you for your help!

They were apart for about 2 days before reintroduction. I nipped it in the bud because I sensed the unrest immediately. They have been back together for about 3 weeks now, but it seems to be getting worse in terms of chasing and bullying. As for the hierarchy, my interpretation before the separation from top to bottom was Eevee (Sick Pig), Daisy (One getting bullied), Luma (neutral), and Jinx (new pig). Jinx does not seem to be bothering Eevee or Luma so my new interpretation seems to be Eevee, Luma, Jinx, Daisy. Daisy seems to be eating just fine still, but I will monitor her weight more closely to make sure she is not losing weight.

 

[Swissgreys]

When you have a group of piggies living together it is perfectly normal for the hierarchy to change over time.
A new pig who is young is unlikely to cause any problems when entering a herd - they just want be accepted.
However when the herd dynamic shifts (such as in the case of a medical separation) the younger piggy who now feels more established in the herd, may make a bid to raise their position in the hierarchy.

Guinea pig social interactions are very complex and can be quite subtle.
It can also look (to us) quite 'mean' or rough, when in actual fact it is just guinea pigs sorting things out in the only way they know how.
It is important to keep a close eye on everyone and monitor the weights of all of the piggies weekly.
An ongoing weight loss can be the early warning sign of true bullying.

It is also important to keep the cage as 'open' as possible - avoid single entrance hides and offer multiple water bottles, pellet bowls and scatter feed veg.
I hope your girls settle down again soon, but given the large cage you have you could always split this into two and have 2 pairs living alongside each other.