Numbers of animals

cagesBritish law protects vertebrate animals such as mammals, fish and birds used in scientific and medical research. The number of procedures on these animals are counted by the Government every year.

Under the Animals (Scientific Procedures) Act, 1986, every regulated procedure on a ‘protected animal’ conducted in Great Britain must be counted - this includes, all vertebrate species (except those in first half of  foetal, larval, embryonic stage) and cephalopods (e.g. octopuses, squid and cuttlefish). These figures are published annually in an annual report by the Home Office (Northern Ireland counts separately and an annual report is produced by the Department of Health for Northern Ireland).

Invertebrate animals such as fruit flies and worms are used in large numbers in research but are not protected by the law or counted.


Number of animals used in 2018

In 2018, there were 3.52 million procedures (3,520,000) on animals, a fall of 7.0% compared with 2017. 

Source: Home Office, Annual Statistics of Scientific Procedures on Living Animals, Great Britain 2018: data tables, Table 1.2 Notes: Specially protected species are Cats, Dogs, Horses and Primates. 



The most common species used in procedures were:

  • Mice - 2.11m procedures 
  • Fish - 0.60m procedures 
  • Rats - 0.32m procedures 
  • Birds - 0.28m procedures 


Together these four species accounted for over 94% of all procedures in Great Britain. Additionally there are four species which are granted special protections in Great Britain. These are:

  • Horses and other equids – 10,424 procedures
  • Dogs – 4,481 procedures 
  • Primates – 3,207 procedures 
  • Cats – 159 procedures 


Trends over time

The number of animals used in research grew steadily from 1939 to the mid 1970s, where it peaked at approximately 5.5 million experiments. The numbers then declined steadily until around 2000, at 2.6 million procedures (a slight change to the counting methodology took place from 1987). Since then, the numbers have risen up around 4 million, before levelling off. It is unclear where this levelling is a permanent state, or whether future numbers will go up or down. The most recent rises in animal procedures appear to mainly be due to the increased production and use of animals with genetic modifications or defects (many fall into the 'breeding' category). The numbers of genetically normal animals have, on the other hand, been dropping steadily – as can be observed in the graph below.

Animal numbers in research 1939 to 

The total number of animals used in research is affected by many factors. The overall funding for life sciences in the United Kingdom, as well as the relative funding in other countries, will change the amount of science done – a proportion of which will involve animals.

More information from the annual statistics (2017 - to be updated)

The annual statistics produced by the Home Office every year are the most comprehensive of any country in the world. They provide information on species, use, genetic status, country of origin, disease areas studied, and much more. Below we offer some of the interesting statistics that can be found in the statistics, as well as a reference to where they are in the reports.

  • The purposes of procedures were as follows: 28.5% was ‘basic research’, 12.5%  was for regulatory purposes, 8.6% was ‘translational/applied research’, 0.7% was for the ‘protection of the natural environment’, and 0.1% was for uses including ‘preservation of the species’ and ‘high education or training’.Severity of animal procedures GB 2016 Together these make up the 51.4% categorised as ‘experimental procedures’. The remaining 48.6% of procedures on animals is for the ‘creation & breeding of genetically altered animals that were not used in further procedures’. [Table 1]
  • All primates were F2 or greater, or from a self-sustaining colony, meaning that no monkeys were either caught from the wild, or an offspring of wild-caught monkey. [Table 2.2]
  • Since 2014 there has been retrospective reporting of animal suffering in every experiment. In 2016 this showed that, across all procedures, 38.4% were sub-threshold, 4.0% were non-recovery, 37.7% were mild, 16.0% were moderate, and 3.9% were considered severe. [Table 3.1 and Table 8]
  • 64.9% of all procedures in 2016 involved genetically altered animals; this breaks down as 50.4% genetically altered without harmful phenotype, and 14.5% genetically altered with a (potentially) harmful phenotype. [Table 4 and Table 8]
  • No animals were used for the testing of cosmetic products or ingredients, as this is illegal under UK law. [Table 7.2]


Not in the statistics

Invertebrate animals such as fruit flies and nematode worms are not covered by the Animals (Scientific Procedures) Act, 1986. The reason for their exemption is that there is a lack of evidence that these animals can suffer, particularly in consideration of the different level of complexity of their central nervous system relative to that of vertebrates. The only exception to this is cephalopods (e.g. octopuses, squid and cuttlefish) which were added to the act as a result of EU Directive 2010/63. While the evidence that cephalopods can suffer is mixed, they were added on a ‘benefit of the doubt’ basis. No country in the world counts the invertebrates it uses in research.

Chimpanzees, orang-utans and gorillas have not been used in the UK for over 20 years and their use has been banned since 1986.

Animals that are killed in the research setting without ever having undergone a regulated procedure are not included in the statistics. This includes animals bred for tissue samples, animals bred for research that could not be used, animals used to sustain inbred colonies, and animals used for health screening of other animals in the laboratory. These animals are referred to as “additional” and reporting requirements in EU Directive 2010/63 require that every five years each EU country must submit details of these animals. Details of additional animals are being reported for the first time for 2017. For more information, click here.

Statistics from Northern Ireland

Animal research in Northern Ireland is monitored by the Department of Health for Northern Ireland. The most recent returns show that 22,508 procedures were conducted on animals in 2015. While mice remain the most common species used (65% of the total), pigs, sheep and cattle together account for 15.8% of research, reflecting the large amount of agricultural research conducted in Northern Ireland. The overall figures for Northern Ireland account for only 0.5% of the total number of procedures for the whole UK.

International estimates

Trying to estimate the numbers of animals used in research worldwide is difficult because many countries do not provide comprehensive statistics.