Rat Tickling Background & FAQ

Yes, the majority of the available evidence (more than 56 different tickling experiments from more than 32 publications) indicates that tickling is beneficial for rat welfare (LaFollette et al, 2017). This is based on their production of positive vocalizations, approach behavior, measures of anxiety and fear, and handling outcomes. Of course, there may be specific models or individual rats that may not benefit from tickling. Ensure that you have properly learned how to read your rat and taken the Rat Tickling Certification Course before attempting tickling.

Unfortunately, most measures of physiology (i.e., corticosterone, heart rate, etc.) are more strongly linked to arousal versus a negative or positive emotional state. For example, elevated glucocorticoids can be linked to pleasurable activities such as sex, hunting, and excitement, and have previously been found to have contradictory results between studies (Dawkins, 2006). For rat tickling, in particular, many rats show increased activity and vocalizations before tickling which could indicate higher arousal and be linked to higher fecal corticosterone.

That being said, other physiological, genetic, and cellular effects of tickling have been positive (LaFollette et al, 2017). Research show that tickling increases dopamine release in the nucelus accumbus as well as decreases adrenaline and noadrenaline after fear conditioning. Tickling also increased adult hippocampus cell proliferation (associated with depression), increases neurogenesis in the dentage gyrus of the hippcampus, and up-regulates production of kallikrein family of mRNAs.

It depends, but is usually likely positive.

It really depends on your research model & we simply do not know for many of them for sure. However, in general, tickling is likely to reduce stress from handling and increase positive affect. Thus, it should make tickled a more valid, representative, and generalizable model.

If you are working with a model related to stress, sociability, psychiatric, or neurological disease, tickling could be used to elicit ultrasonic vocalizations as a useful outcome measure or covariate.

Rats subjected to chronic mild stress or chronic variable stress show decreased 50-kHz vocalizations in response to tickling. Tickling can therefore be used to determine if your intervention is working. Furthermore, USVs measured during tickling could be used as a covariate during tests related to behavior. There is evidence that USVs during ticking predicts anxious-like and depressive-like behavior. That is, rats that make more 50-kHz calls during tickling have less susceptibility to chronic stress as well as less generalized anxiety and fear. Finally, USVs during tickling are moderated by psychopharmalogical intervention.

Please see the Handbook of Ultrasonic Vocalization: A Window Into the Emotional Brain for more information on how to use rat tickling and 50-Khz vocalizations as a validated outcome measure of positive emotions.

It is not necessary to have ultrasonic monitoring equipment in order to effectively tickle rats. You can observe your rat’s behavior to determine if they are responding positively. That being said, 50-kHz ultrasonic vocalizations (USVs) are the BEST and most objective measure indicating positive emotions.

If you are on a budget, but still interested in validating your technique (or just quantifying background USVs) we recommend the Magenta Bat Detector which is about 64 British pounds. (If you sell a comparatively priced piece of equipment please let us know and we will list it here). The disadvantage to this piece of equipment is that it doesn’t actually record USVs (just transmit them in real-time) and can only transmit a narrow range at a time. For example, you cannot use it to listen for both 50-kHz and 22-kHz USVs at the same time.

We do not have evidence if background USVs impact tickling success, however computers and video equipment which both create ultrasound have been used in tickling study with good success of the tickling technique.

If you have an ample budget or are looking to quantify USVs as an outcome or moderating factor then there are many options for equipment. One the Gaskill laboratory used the Ultramic 200K and Seapro analyzing software.

Tickling can be flexible depending on your study constraints. However, research shows that tickling each rat for 15s for 3 days is the minimum effective dosage (LaFollette et al., 2018). In that study, rats were tickled 3 days after being shipped and were tickled for 3 consecutive days and then just before an intraperiotoneal injection on the 4th day.

However, in that study group’s experience, the 3 tickling sessions/days do not need to be consecutive. In fact, even across 3 sessions on the same day spaced about an hour apart, rats show significant gains.

After the 3 initial tickling sessions, it is recommended to tickle rats as study procedures and staff allow. This could include before procedures or before cage change. If time is an issue, aim to tickle about a month. There is evidence that the beneficial effects from tickling are persistent for at least 4 weeks after tickling is discontinued (Cloutier et al., 2013) although that may depend on what sort of procedures are done in that period.

Note that rats should be tickled BEFORE rather than after stressful procedures (e.g., injection). Although some may think that tickling would be a good “reward”, many procedures cause a bit of discomfort that seems to make tickling less rewarding. Rather, tickling is used to change the emotional state of the rat and improve the human-rat relationship.

Not if you truly want to tickle rats. Rat tickling mimics rat rough-and-tumble where the pin is a key component. In some instances, it seems that rats can get more fearful of humans if they are ONLY “tickled” on the back of the neck, because they do not interpret that as play.

Review the practical implementation section of the Rat Tickling Certification Course. There are extensive pictures, videos, tips and tricks on how to accomplish tickling.

The short answer is no. Rat tickling is an intervention specifically designed to mimic rat natural play behavior. The social play of mice or other animals differs from rats and we currently do not have a technique to mimic it. Certainly rat tickling does not.

However, if we can find ways to mimic social play or induce play generally this could hold promise for other species.

The best age to tickle rats is when they are juveniles (21-63 days old), just after weaning. The tickling response is stable from 44-71 days and drops off at least through 148 days.

Are they less than 3 months old with minimal negative handling experiences? Then yes!

Although tickling juvenile rats is best, adult rats still benefit from this interaction. Previous research shows benefits for adult rats (3-month old) from tickling.

Did they receive tickling as juveniles?

Rats tickled as juveniles were again tickled at 6 months old with beneficial success. However, pay attention to your individual rats responses. Depending on what experiences they have had in between these time points they may respond more positively or neatively.

Are they older than 3 months, with minimal handling & no tickling previously?

If so, use caution and pay attention to individual responses. These rats may not be prime receptive age for tickling and little research has been done in this age group. We do know older females are likely to respond better than older males. Additionally if they have had extensive other positive handling they are more likely to respond better.

Are they older than 3 months, have had negative handling experiences, and currently show aggressive/defensive behavior?

In this case, we recommend waiting to try tickling with a new group of rats. Tickling is best used as a preventative/initial experience versus a rescue treatment.

Thus far, tickling does not show differences between common rat strains/stocks. No difference in USVs during tickling has been found between male or female Long-Evans, Sprague Dawley, and Wister rats (Schwarting, 2018a & Schwarting, 2018b). Tickling has also been used successfully with Fisher rats. 

We do know that USVs during tickling have a genetic component (LaFollette et al., 2017). You can breed rats to vocalize more or less for tickling. Rats vocalizing less have been used as a model for autism spectrum disorder.

No, tickling IS acclimation.

There is no need to otherwise habituate or acclimate rats to human contact before tickling (assuming you are using juvenile rats that are relatively naive to handling ). Rat tickling is habituation in a way that rats understand. You do not need to do any other gentling, stroking, or otherwise. Just don’t expect rats to initiative contact right away.

If you do have extra time, you could allow rats to explore your passive hand for a few days before tickling.

Research is mixed (LaFollette, et al. 2017)

Some studies find juvenile males make more vocalizations and some studies find the opposite. It’s possible there is an interaction between handler and rat sex. We do know that rats mask pain in the presence of male humans (Sorge et al., 2014), perhaps they also mask positive responses?

It does appear that for older adult rats, females respond more positively than males.

Did they receive tickling as juveniles?

Rats tickled as juveniles were again tickled at 6 months old with beneficial success. However, pay attention to your individual rats responses. Depending on what experiences they have had in between these time points they may respond more positively or neatively.

Are they older than 3 months, with minimal handling & no tickling previously?

If so, use caution and pay attention to individual responses. These rats may not be prime receptive age for tickling and little research has been done in this age group. We do know older females are likely to respond better than older males. Additionally if they have had extensive other positive handling they are more likely to respond better.

Are they older than 3 months, have had negative handling experiences, and currently show aggressive/defensive behavior?

In this case, we recommend waiting to try tickling with a new group of rats. Tickling is best used as a preventative/initial experience versus a rescue treatment.

Yes. Published research shows that it is beneficial to tickle rats before injection even when they are given these injections once a day for 10 days. We also have heard positive reports of tickling rats prior to surgery, implants, etc. Tickling will help reduce the overall stress of handling even if the procedure is negative. You may need to tickle more to counteract these procedures. Be sure to tickle BEFORE procedures as rats may be too sore after a procedure to play.

Regardless, you know your rats best. Assess their behavior and response. Some rats could become too stressed to benefits from tickling.

Yes. Tickle them prior to implantation or surgery. This will help establish an initial positive human-rat relationship. It may even decrease the overall stress of these procedures. Afterward, use your best judgment to ensure you do not disturb the implant or surgical site. You may need to discontinue tickling or only do occasional dorsal contact.

There is some evidence that single-housed rats may enjoy and perhaps even need rat tickling more. After all, single-housed rats are deprived of social interaction with other rats and tickling may act as a refinement. Tickling may have a higher reward value to these rats.

However, a few studies comparing solitary and group-housed rats where rats were kept together during tickling did not find differences in vocalization rates. Therefore, unless you need to collect data on vocalizations, it may be beneficial to tickle cage mates together. That being said, tickling is still quite effective on separated animals.

Have you already tickled for 3 days?

Try to confidently tickle rats for at least 3 days before formally assess their response, unless working with a rat in distress. Sometimes it takes the rats time to ‘get’ the procedure. During this time, your rat is likely still gaining habituation & handling benefits from tickling.

When tickling, make sure you are confident and assertive. The more hesitant you are, the more time it will take the rats to figure out that this fun and you are playing!

After 3 days, are there negative responses?

It’s recommended to continue tickling occasionally  unless there are continued negative responses (e.g., 22-kHz vocalizations, defensive posturing, avoidance/freezing, tail rattling). If there are, you may want to discontinue tickling for this individual rat. Use your best judgement.

Ideally, whoever is performing any aversive procedures (e.g., injections) or regularly handle rats should tickle them. This should counteract some negative procedure effects. Consistency could be beneficial if there is planned to be one regular caretaker for the particular group of rats. 

However, if this is not possible or practical then anyone could tickle rats. There is some evidence that rats generalize tickling and a positive human-animal interaction to other individuals. Furthermore, if several different individuals will be tickling rats then being tickled by multiple individuals could help them generalize.

“Tickling” is just a name. Most researchers don’t think that tickling is equivalent to human tickling, especially of adults. Rather, it mimics aspects of rat rough-and-tumble play behavior. Other terms for the technique include playful handling, heterospecific rough-and-tumble play with rats, etc.

Still, some rats like tickling less than others. These rats give off fewer positive vocalizations overall, but most don’t seem to find it negative, just less positive. They still receive welfare benefits. Regardless, we recommend you use your best judgment and read your rat.

Yes, to follow personal protective procedures and avoid animal allergens you should wear gloves. There is no evidence that rats prefer a bare versus gloved hand and a gloved hand will transfer better to procedures and other humans.