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I’m afraid a 100cm cage is too small and is unsuitable to be used for guinea pigs at all, it’s not suitable even for short periods. It’s rather a big issue that they are still sold and worse that they are sold as suitable for piggies.
A ferplast 120 is unfortunately also too small for two boars (a 120 is considered minimum space for two piggies but that is aimed more at sows with their slightly lesser territory needs)
Boars are very territorial and need a lot of space at all times. Lack of space can be a contributing factor in boar fall outs (the main cause being character incompatibility) and a 120 would quickly become too cramped particularly for teen boars. If a fight was to occur then the piggies would need to be permanently separated.
Two boys need 180x60cm at all times but there are no commercial cages which are that size. The closest you can get is a ferplast plaza 160 - obviously that is 160cm so still a bit below what is needed (150cm is considered minimum for two boars but for some pairs and particularly teens it can still be too small) but it is the best you can get in terms of a commercial cage for boars.
Owners of indoor piggies usually use c&c cages and that is especially important for boars.
Two boars would need a 5x2 c&c cage - so that means five grids by two grids which measures 180x70cm.
Cage Size Guide
It is also very important to keep in mind that as boars are territorial, any change in environment will disrupt their territories and can set them off in a dominance dispute while they reestablish. A lot of pairs can move from one cage to the next, provided the cage they are going to has not been cleaned out before they go back in . But in some pairs and particularly very sensitive teenagers, it can have a big effect and happen every time they are moved (and the reestablishing process can take two weeks so moving frequently can be disruptive in very sensitive teens).
To that end - and regardless of whether they are moving cage - it is not recommended to clean the whole cage in one go, instead clean half one day and the other half the next day. Doing a full clean in one go removes all their scent and means they won’t recognise it as their space, causing dominance and scent marking. Cleaning half at a time means scent remains (and by the time you clean the dirty half, they have remarked the cleaned half) so they always recognise a cage as their territory
Reacting to group or territorial changes: Dominance and group establishment/re-establishment
This is another helpful guide about boar specific care
A Comprehensive Guide to Guinea Pig Boars
Piggies do need to be kept warm and anything below 15 degrees is considered too cold, so keeping them inside at night* is a good idea if you aren’t able to keep their hutch warm enough with snugglesafe heatpads and thermal covers. They do still need lots of space though
* It is important to add that piggies cannot be exposed to sudden and large temperature swings (5 degrees or more is considered a large swing) as their bodies can’t cope and it can make them ill. So while it is ok at this time of year for them to be outside during the day and inside at night (as the temp between outside day and inside night will be about the same), that won’t be the case all year.
In autumn and winter, it will be colder outside than inside so piggies who live outside cannot be brought into the house (or live inside cannot be taken outside) at all - they either need to stay inside all winter or outside all winter (also meaning outdoor living piggies cannot come indoors for playtime during winter daytimes).
Further, in spring for piggies who have been inside during winter, they must be acclimated to outside temps slowly - so as you are with doing with outside during the day once daytime is over 15 degrees but back inside at night until all risk of frost has passed and nights are warmer. Then they can stay in a hutch outside during the night too.
Do be aware that in mid summer, hutches become dangerous. They trap heat and heat up very quickly even in the shade (more than outside air would suggest) so use a thermometer on the hutch and ensure piggies are not outside at all once it is over 25 degrees
Hot Weather Management, Heat Strokes and Fly Strike
