Temperament of rats in shown in studies to be 40-60% genetic and 40-60% environmental. I do not interact with baby rats for longer than necessary to clean the cages, check for milk bands, or take a quick photo until I begin temperament testing. This is to avoid environmental effects on temperament and to evaluate the true genetic temperament of the rat to ensure a temperament sound animal is produced. This is what breeders refer to as avoiding “temperament masking.” Baby rats held daily will be used to human contact and will make environmentally temperament sound pets, but as soon as they go a few days without being interacted with, they will show their true genetic temperament and can become aggressive or fearful biters. It’s essential for breeders to understand the true genetic temperament of their lines to ensure they improve upon the species and don’t adopt out aggressive or fearful rats.
When it comes to temperament testing at Moomoo Rattery, I begin interacting with the babies around 2.5 to 4 weeks of age. My somewhat rigorous approach to temperament testing ensures that I never adopt out overly skittish, aggressive, or non-human-oriented rats. My goal is to breed pet-quality rats, as close to perfect as possible, while acknowledging that these are still animals with instincts of self-preservation. While I don’t blame prey animals for being afraid, I strive to make sure that every adopter’s experience is a positive one. After all, most people don’t want a pet that wants nothing to do with them.
The process includes exposing them to restrained handling, such as picking them up in one hand, scruffing, leaning them back, lifting them in various ways, and touching their face, belly, feet, tail, and back. I also introduce them to unfamiliar environments and rats. Additionally, I test how quickly they grab food from my hands to assess whether they would be suitable for children. While they eat, I gently mess with them to ensure they don’t show signs of food aggression.
Throughout this process, I evaluate their overall reactions to humans and human hands, curiosity, and braveness, observing if they improve with continued interactions. I use a "three strikes, you’re out" method, meaning any concerning behavior that persists through multiple tests will affect their adoption or breeding status. Biting other rats or humans is the only exception and that only takes 1 instance before removal. For the minor failures, judging a rat based on a single interaction is not fair as some rats simply have bad days. I also assess how they recover from loud and common household noises, like vacuums, loud conversations, and TV or music. To make sure they aren’t just familiar with my voice, I have my husband come in and talk to them as well. Observing their reactions when I’m messing around in their cage is also part of the assessment.
Rats that display fear poops, squeak when handled, bite beyond curious nibbles, flail themselves to the floor when picked up ("suicide jumpers"), are overly squirmy, or cower and run away despite weeks of daily handling are not immediately put up for adoption and certainly not considered for breeding. Since temperament is closer to 60% genetic in my lines, the minor “failed” rats are kept for an additional two weeks and exposed to heavy handling in an attempt to rehabilitate them. If they improve, they are considered for adoption with the next round and the adopter is made aware of their temperament history.
The rats that score the highest in temperament testing and display the calmest behaviors are kept back for breeding. They continue to undergo temperament testing throughout their lives and are removed from the breeding program if any issues arise as they mature. Hormonal and maternal aggression, which often appears between 5-12 months or after 1-2 breeding cycles, means testing never truly ends. I frequently introduce unfamiliar rats to ensure that the rats I adopt out are friendly enough to integrate with other rats, should their owners choose to introduce new pets.
If you adopt a rat that is not adjusting well or does not get along with your other rats, I will do everything I can to help and make the situation right. I always recommend letting new rats settle for 24-48 hours in their new environment before interacting with them to reduce stress. A 2 week quarantine period is also recommended before introducing new rats to current rats. Temperament can’t always be guaranteed as every animal is an individual but this process lowers the risk of issues unlike adopting from a feeder or pet store that does not conduct any sort of temperament testing.
Check out my blog on bonding with rats or where to get pet rats for more help!
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