The rhythms of rats
For quite a while now I have been letting my rats out twice a day for exercise, once in the morning, once in the evening. I have really noticed a big difference in their activity levels since doing this!
At one point I used to feed them early evening and then let them out later evening after a full bellied snooze, but now I put them out first (9pm ish) for an hour and then feed them after, as they still didn't do that much in the evening and I figured it was because they were still digesting...
But no, it seems I just have morning rats! They come out after a quick breakfast and are manic! They are far more active on their morning runs, and much less likely to hide behind their mattress and sleep! Even Opal with run about and play and interact more. They pile in the boxes, chase each other round, scale up the mattress and enjoy games of tag and chase with me. In the evening they do this too, but to a lesser extent, and some nights it's impossible to get any movement out of lazy Opal at all!
All 5 are more likely to just climb up on top of the mattress and perch their, or climb onto my shoulder and rummage in my pockets.
At night they sometimes start 'asking' to go home after just half an hour, but they stay out happily in the morning for up to a couple of hours with just a bit of apple or a bowl of water for moisture. They are hyper with adrenalin for longer after going back in the cage in the morning too.
When I first read Julia’s account of her rats’ behaviour I was intrigued to think how (if this was a general trait) it could be utilised to help weight loss in obese rats. Using up more energy than you take in is the key to reducing obesity in rats, and the kind of energetic activity Julia describes would not only use up calories, but also raise the metabolic rate, thus using up more energy even at rest and during sleep. It is certainly something worth trying if you are fighting with fat ratties - along with modifying their diet of course.
Considering these traits led me to thinking about (and then investigating) the natural biorhythms of the rat.
Wild rats are often thought to be nocturnal, being the most active during darkness, but they actually have three periods – dusk, just before dawn, and one in-between – when they are at their most active. Some low ranking rats will also venture out during daylight hours, especially if more dominant colony members have deprived them of food.
All mammals have an internal ‘body clock’ – a bundle of nerve fibres in the hypothalamus (an area of the brain that regulates metabolic processes and autonomic responses within the body). By these processes this ‘master clock’ controls ‘mini-timers’ in all the major body organs causing the natural rhythms we experience. For instance – have you ever wondered why you get tired at bedtime? This is because a hormone called melatonin is released (under the influence of the ‘master clock’) which induces sleepiness. The same hormone can also suppress libido, accounting for a female rat’s tendency to come into heat less frequently during the short, dark days of winter. Rats kept in artificial light to extend daylight hours will breed all year round.
The main external factor that affects the ‘master clock’ is light input via the eyes. Although our rats do not have very good vision even the pink-eyed varieties are well able to distinguish light from dark. Activity, exercise, temperature, noise and the timing of mealtimes also affect it. This effectively means that by manipulating our captive rat’s environment (for example, lights coming on, on a dark evening) we can change their periods of wakefulness.
Rats are often at their most active (because hormones are flowing in response to stimulation from the ‘master clock’) when they are anticipating food. During this period their temperature increases, and there is increased production of digestive enzymes in preparation for consuming their meal. Because of this you will find your rats are more interactive and energetic if you give them time out before you feed them.
All body functions are affected by these rhythms, for example a rat’s sensitivity to pain is highest during the hours of darkness, and lowest during the transition from light to dark (dusk). This would suggest that when giving daily painkillers like Metacam post-operatively it is appropriate to give them in the evening.
Interestingly aging rats show a disruption to the regularity of the ‘master clock’. They often have fragmented biorhythms – and will nap when younger rats are active, and remain wakeful when the youngsters are snoozing in their hammocks. Much like people really!
Author: Julia Hands and Alison Campbell
Articles relating to rat behaviour
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