The University of Southampton openly shares the numbers of animals used in procedures under the Animals (Scientific Procedures) Act 1986 (ASPA) as part of its commitment to the Concordat on Openness on Animal Research in the UK .
Researchers and technicians at the university take every step to ensure that animals experience as little pain and distress during any experimental process as possible.
The table below shows the reported numbers and rounded percentages of animals used at the University of Southampton under ASPA for the previous five calendar years.
| The number of animals used in procedures Under ASPA | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Species | 2021 | 2022 | 2023 | 2024 | 2025 | ||||||
| Mice | 12,055 (99%) | 12,083 (98%) | 11,151 (98%) | 10,726 (93%) | 8480 (95%) | ||||||
| Rats | 13 (<1%) | None (0%) | None (0%) | None (0%) | 0 (0%) | ||||||
| Fish | None (0%) | 220 (2%) | 172 (2%) | 696 (6%) | 343 (4%) | ||||||
| Rabbits | 3 (<1%) | None (0%) | None (0%) | None (0%) | 0 (0%) | ||||||
| Chicken Embryos | 128 (1%) | None (0%) | None (0%) | 43 (<1%) | 137 (1%) | ||||||
| Xenopus tropicalis (Tadpoles) | None (0%) | None (0%) | None (0%) | 19 (<1%) | 0 (0%) | ||||||
| Total | 12,199 | 12,303 | 11,323 | 11,484 | 8960 | ||||||
Procedures carried out on animals for a scientific purpose are considered regulated procedures only if the severity is above the threshold defined as equivalent to the pain, suffering or distress caused by the procedure carried out.
All research must have a Procedures Project Licence (PPL) which explains the research, the harms to the animals and the benefits to society. The PPL has protocols and each protocol has a maximum severity assigned to it. These severities are: ‘sub-threshold’, ‘mild’, ‘moderate’, ‘severe’ or ‘non-recovery’. Please find a more detailed description of these categories below:
Severity categories
Sub-threshold: It is possible that procedures authorised under a project licence could result in below threshold severity. Procedures will be deemed sub-threshold when the procedure in retrospect did not cause above threshold pin or suffering, for some or all of the animals involved. Examples of where sub-threshold may be given is: the breeding of genetically altered animals under PPL authority but without a harmful phenotype, or dosing with a compound in feed where the animals ate normally and suffered no consequences of being dosed etc.
Mild: Any pain or suffering experienced by an animal is, at worst, only slight or transitory and minor so that the animal returns to its normal state within a short period of time.
Moderate: Moderate procedures cause a significant and easily detectable disturbance of an animal’s normal state, assuming that appropriate monitoring systems are in place and that they are used by trained and competent staff.
Severe: These cause a major departure from the animal’s usual state of health and well-being. It would usually include long-term disease processes where assistance with normal activities such as feeding, and drinking are required or where significant deficits in behaviours/activities persist.
Non-recovery: When the animal was under a general anaesthetic for the experiment and was not.
Further information on severity threshold can be read here .
The table below shows the numbers of animals used at different severity categories for procedures under ASPA over the last five calendar years.
| Actual severity of animals used in procedures under ASPA | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Severity | 2021 | 2022 | 2023 | 2024 | 2025 | |||||||
| Mice | Rats | Rabbits | Mice | Fish | Mice | Fish | Mice | Fish | Xenopus tropicalis (Tadpoles) | Mice | Fish | |
| Sub-Threshold | 5,065 (42%) | 0 (0%) | 0 (0%) | 5,203 (43%) | 0 (0%) | 5,372 (48%) | 0 (0%) | 4,876 (45%) | 0 (0%) | 0 (0%) | 3719 (44%) | 0 (0%) |
| Mild | 4,316 (36%) | 0 (0%) | 0 (0%) | 3,906 (32%) | 220 (100%) | 2,851 (26%) | 172 (100%) | 2,739 (26%) | 576 (83%) | 19 (100%) | 2020 (24%) | 343 (100%) |
| Moderate | 2,474 (21%) | 11 (85%) | 3 (100%) | 2,888 (24%) | 0 (0%) | 2,809 (25%) | 0 (0%) | 2,998 (28%) | 120 (17%) | 0 (0%) | 2601 (31%) | 0 (0%) |
| Severe | 128 (<1%) | 0 (0%) | 0 (0%) | 64 (<1%) | 0 (0%) | 33 (<1%) | 0 (0%) | 25 (<1%) | 0 (0%) | 0 (0%) | 35 (<1%) | 0 (0%) |
| Non-Recovery | 72 (<1%) | 2 (15%) | 0 (%) | 22 (<1%) | 0 (0%) | 86 (<1%) | 0 (0%) | 88 (<1%) | 0 (0%) | 0 (0%) | 105 (<1%) | 0 (0%) |
| Total | 12,055 | 13 | 3 | 12,083 | 220 | 11,151 | 172 | 10,726 | 696 | 19 | 8480 | 343 |
A breakdown of research animal numbers (nature of use) 2022
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A breakdown of research animal numbers (nature of use) 2023
A breakdown of research animal numbers (nature of use) 2024
A breakdown of research animal numbers (nature of use) 2025
The above data is collected and returned to the Home Office at the end of January each year. The figures for the number of animals used in procedures and severity thresholds for the previous year will be updated on this website as soon as possible, once figures have been sent to the Home Office.