We need to discuss this, its been happening a lot lately and throwing rookie keepers off.
I've been seeing a lot of inexperienced keepers(no offense, I made the same mistakes in the past) mistaking a chams puff threat response for gravidity. The pictures below are of a male and a gravid female but the point is the same, both are displaying their instinctive(IM TALKING TO YOU JO! lol) puff threat response.
Lets start with Roux(blue male Nosy Be) - the giveaway that he isn't gravid(besides obviously being male) is how thin his belly is from vent to half way between his rear and front legs. If we froze him where he is and looked up from beneath him he would appear to be about 3/4" wide vent to front legs. Very consistent.
Now onto Momma who is currently gravid - She is in full threat puff display just like Roux. Now if we froze her and looked up at her from below exactly as we did with Roux she will be MUCH thicker from vent to midway between rear and front legs and gradually thinning as we look closer to the front of her front legs. Obviously this is due to her being gravid and carrying eggs just forward of her vent. This is a dead giveaway she's gravid, you can also see the lumps along her sides but this can be more troublesome to identify early on.
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