Transporting two rats together: 22 kHz distress calls don’t scare every rat, a study shows
Published by Planète Pets · managing editor: Clément Lacaille · how our guides are written
A companion generally lowers transport stress in rats, as shown by a study already covered on this site. Another piece of research, focused on ultrasonic distress calls, complicates that picture: a terrified companion does not always reassure, it can also broadcast its own fear. Our other travel guidance is gathered in the rodent travel and safety section.
Contents · 5 sections
A sender-receiver design built around 22 kHz calls
Kim, Kim, Covey and Kim published a 2010 study in PLOS ONE on the social transmission of fear in rats through ultrasonic distress vocalizations around 22 kHz, inaudible to the human ear (see the study). The design used two roles: a "sender" rat, fear-conditioned through an earlier aversive experience, then placed with a "receiver" rat in an unfamiliar space. The researchers measured whether hearing the sender's calls was enough to trigger freezing, a classic fear response, in the receiver.
Only already-stressed receivers freeze
The central finding: the sender's 22 kHz calls reliably triggered marked freezing in receiver rats that had themselves already been through an aversive event in the past. Naive receivers, with no prior aversive experience, stayed largely unaffected by the same calls. Vocal fear contagion, then, does not simply depend on proximity to a stressed companion: it depends, perhaps mostly, on the listening rat's own history.
What this means for a two-rat trip
This result is a reason to qualify the idea that a calm rat automatically shields a stressed companion throughout an entire trip: a rat that has never been through anything unpleasant does seem largely unresponsive to another's distress calls, but that is not necessarily true of a rat that has already had, say, a rough first vet visit. For that animal, sharing a carrier with an already-panicked companion could reinforce its own fear rather than ease it. In practice, it is worth pairing a first-timer's earliest trips with a genuinely calm companion, and staying alert if either rat already carries a bad transport memory.
The study's limits
The experiment was run in a lab, with fear conditioning induced by a mild electric shock, a method far removed from an ordinary car ride: carrying this over to everyday transport remains a reasonable extrapolation, not a direct measurement. The study also does not say how long this "sensitive receiver" status lasts after a first aversive event.
Frequently asked questions
Can a rat with no stressful history "catch" a companion's fear?
According to this study, not much, or at least far less: it is the rats that have already been through an aversive event that react most to a cagemate's distress calls.
Should a rat always travel with a companion?
Yes in most cases, a companion's presence remains broadly calming; this study simply suggests avoiding pairing an already-stressed rat with a very distressed companion. Find all our guides on the rodent hub.
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This guide is part of Planète Pets’s Rodents universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.
