UPDATED: How many animals are used?

A question we get asked regularly is how many animals are used in experiments.  Figures are often hard to obtain, although as a UK-based site we will look at UK statistics in detail shortly.

Estimates exist that 100 million animals are used wordwide, which is about 274,000 per day, or three every second.  However, this estimate is for vertebrates only.

It is estimated that the European Union uses around 10.5 million vertebrate animals each year: 28,800 per day or one every three seconds.

The US has been very poor at recording the number of animals used, and does not officially record the total of rodents.  A midpoint of estimates is 18.5 million per year, which is 50,700 per day, or one every 1.7 seconds.

The UK

Official statistics are compiled in the UK and made available on the Home Office website.  As we show below, there are many problems with these statistics.  The latest statistics show animal use in 2011, which totals 3,792,857 animals.  This equates to 10,391 per day, or one every 8.3 seconds.

This indicates that the UK is responsible for 35% of animals used in the EU.


However, this statistic is misleading for several reasons.  One factor that certainly causes massive distortion is overbreeding.  Rats and mice breed easily, and often individual labs will maintain their own breeding colonies of several different strains.  Demand for these may be unpredictable, and they therefore breed more than they expect, and kill the rest.

For some strains, demand will be very low.  But it will not be possible to only provide these low numbers of mice and still provide enough future adults to continue breeding and avoid inbreeding.

Statistics obtained from a London Medical School in 1994 showed that over a long period 2.2 mice and rats wer killed as surplus to requirements for every one that was used in experiments.  Soon afterwards, criticism of similar statistics at a different lab led to the response that this was in line with the rest of the industry.  Based on this, it would be reasonable to expect that mice rats, and many other animals are killed in numbers much larger than those admitted.

Culling is typically done by gassing with carbon dioxide, which is a stressful method that often causes panic and suffering.  This was documented at the medical school mentioned above, which had many problems with both the gassing equipment and the practices used by the staff.

Unsuitable for use

Some animals are bred and will not be wanted or experiments.  For example, 'nude' mice carry a genetic defect meaning they grow no hair.  The animals are born to one nude and one normal parent, which means that we expect 50% of the young to grow hair.  This was observed in practice: the babies growing hair were killed.

Due to the nature of the environment in which they are born and raised, they are killed by crushing the head or hitting it against something hard, not gassing.  These killings were not included in official statistics.

Incidental deaths

Other deaths occur or a variety of reasons.  Unsuitable housing and overcrowding often results in fighting, and deaths have been recorded resulting from this.  Accidents have also been documented.  A typical ones is when a member of staff replaces a lid on a cage of lively mice looking to escape, crushing their heads or necks. 

Escapes have also been noted, meaning it is easier to kill the animals, or that it has become contaminated and needs to be killed.  An adolescent escaped rat was found dead in a glue trap intended for cockroaches.  Unexplained illnesses also cause deaths.  None of these are counted in the statistics.

'Defence' experiments

The Ministry of Defence conducts a number of experiments under secrecy, and these are not covered by the Home Office, and the statistics never released.  The numbers involved are subject to speculation, although at least one MOD lab is known to contain a large primate unit.  These animals are not included in the Home Office statistics.

Recent trends

Then numbers used had been declining since the mid 1970s, but have followed and upward trend since the mid 1990s.  Given that this period was one in which the awareness and emergence of technological non-animal methods sharply increased, this really is inexcusable.

What is the real total?

Due to the reasons above, we can be confident that the official statistics are misleading.  As many animals are not counted, we can't be sure of the total.  However, just including the best estimate of standards overbreeding of mice and rats, we should estimate that over ten and a quarter million animals are killed in UK labs: 28,100 per day, one every three seconds.

Based only on the Home Office statistics, the numbers used include:

7342 per day - one every 12 seconds

1545 per day - one every 56 seconds

744 per day - one every 1.9 minutes

466 per day - one every 3 minutes

103 per day - one every 14 minutes

42 per day - one every 34 minutes

44 per day - one every 33 minutes

Guinea Pigs
32 per day - one every 46 minutes

12 per day - one every 115 minutes

7 per day - one every 3 1/2 hours

5 per day - one every 4 hours

14 per day - one every 1 hour 43 minutes

12 per day - one every 2 hours

Gerbils and other rodents
11 per day - one every 2 hours 15 minutes

one every 23 hours

one every 37 hours

The forgotten species

As we detail elsewhere on the site, a major casualty of relying on animal experiments is the human patient.  There is no doubt that humans lose their lives in large numbers due to reliance on data from animals which is terribly unreliable.

The British Medical Journal estimated that 10,000 humans are killed each year by medical drugs.  This is more than the number of dogs, pigs, hamsters, gerbils, other rodents, cattle, deer or primates.

Humans are a major victim of animal testing.