Why it’s Important

to Weigh Your Pet

Image Source: Andreas Lischka

Predator and prey animals are in what is known as an ‘evolutionary arms race’. This means that while prey animals are constantly evolving new traits to avoid being eaten, predators are actively evolving traits that help them overcome the tactics of their quarries. That said, prey must always stay one step ahead of predators to maintain the natural balance. If there were, for example, considerably more foxes than rabbits, the rabbits would be hunted to extinction and then the foxes would starve.

Even the king of natural predators, the lion, has only a 19% success rate when hunting alone, and around 30% when hunting in a group. To ensure that they bring food home to their cubs, lions – and most other predators – adopt the strategy of selecting the weak link in any group of animals. A young, elderly, sick or injured animal makes for an easier target, and hunting this individual significantly increases a predator’s chances of catching their prey.

So why is this relevant to our pets?

If you’ve ever watched your cat avidly stalk a butterfly, or your hamster stashing food despite having an abundant supply, it will be clear to you that even the most well-acclimatised of pets – those that are fully domesticated – still have some inherent natural behaviours. One of these evolved to avoid being the chosen target of a predator: hiding illness and injury. A prey animal, which is defined as any animal that is hunted and used as food by another animal, will usually attempt to appear as healthy as possible, no matter how unlikely it is that they will be coming into contact with a predator. 

A pet blue budgie being weighed
Here is our beautiful budgie, BB, getting weighed.

How do we tell if our pets are sick?

Learning your pets’ behaviour is a must. Though this is harder with some animals than others, it is always a good idea to get used to your animals’ regular behaviours, noises, likes and dislikes so that you can tell fairly quickly if something has changed behaviourally.

But a far more accurate indicator of their health is weight, especially with extremely small animals where a change of just a few grams could signify a problem. Most sick or injured animals will lose weight due to increased difficulty eating, or a higher energy expenditure as they attempt to continue normal behaviour while healing, so regular weighing will give you the earliest indicator of a problem, even if your pet is trying to hide their symptoms. 

How often should I weigh my pet?

You should weigh your pet regularly and keep a note of their weight each time you do so. Having their weights monitored and written down will help you recognise their regular fluctuations and distinguish between a normal change or a worrying sign. Weighing weekly may be advised for animals that are particularly vulnerable, such as those who are elderly or with ongoing health conditions, provided that the weighing process is not so stressful that it may exacerbate their health concerns. Less frequent weighing is fine for more robust animals. The exact frequency of weighing depends on your comfort level with your pet’s health and how stressful the weighing process may be. Rodents and birds remain particularly vulnerable and I would not advise weighing any less frequently than monthly, but this may not be necessary for a dog or cat. 

A pet Syrian hamster being weighed
And here is our boisterous hamster Bonnie being weighed (using a little treat to ensure she sits still on the scales).

What should I do if my pet’s weight changes?

Vet trips can be stressful for both you and your animal (not to mention costly) but it is far better to be safe than sorry. Keeping a close track of their weight can tell you when it is time to worry, but it can also save unnecessary trips for behavioural changes that might simply be explained by hormone levels or growing older. Anything that worries you, especially with a small delicate animal, should warrant a trip to the vets, but weighing your pets can help you sort out your fears from your legitimate concerns.

If you’re anything like me, you will be constantly worried about the health of your animal. As someone who has very fragile pets, I’m no stranger to rushing my poor animal to the vet for something that turned out to be nothing to worry about. On one particularly embarrassing incident, I even phoned my vet over what I thought was an abnormal lump, but which turned out to be nothing more than part of my bird’s natural anatomy. This is why it can be so useful, not only for your peace of mind but also your pets’ health, to learn all there is to know about your animal, their regular weight, behaviours and preferences. I have become so familiar with that same bird who I took to the vet over me feeling her wing joint that I am now able to feel changes of just a few grams simply by picking her up.


  • Alex Mockridge

    Alex is a passionate animal lover with a background in zookeeping. Parrots have always been her favourites and although she adores all creatures great and small, and has a keen interest in all areas of animal husbandry, our feathered friends will always hold a special place in Alex's heart.

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