Hilda Margaret Bruce (5 April 1903 – 2 November 1974) was a British zoologist, best known for her discovery of the Bruce effect, a pheromonal behaviour observed in many rodent species.^[1] Her work on the control of fertility earned her the Oliver Bird Medal.

Hilda Bruce was born on 5 April 1903. She was educated at St Leonards School.^[2] In 1923, she began her tertiary studies at King's College for Women, where she received a BSc in Household and Social Science, and another in Physiology.^[2] In 1928, Bruce joined the National Institute for Medical Research (NIMR) at Mount Vernon, Hampstead.^[3] Her early research was dedicated towards the understanding of Vitamin D; she also jointly published the first article describing the breeding characteristics of the golden hamster.^[4] In 1933, Bruce was employed by the Pharmaceutical Society, where she continued her research on Vitamin D.^[3][2] In 1941, she was appointed to set up the Cod Liver Oil (Poultry) Standardisation Laboratory. In 1944, she returned to the NIMR, where she formulated specialised diets for laboratory animals.^[3][2]

From the early 1950s, Bruce turned her attentions towards sexual behaviour in rodents, particularly the Whitten effect.^[3] In 1959, she published her discovery of what is now called the Bruce effect, the termination of pregnancy following exposure to the scent of an unfamiliar male.^[5] Bruce retired from the NIMR in 1963, but continued part-time research, variously on nutrients, development and pheromones, at the Department of Investigative Medicine in Cambridge.^[2] She continued work at the Department until 1973.^[2] In her later years, Bruce largely used a wheelchair, having been afflicted with worsening rheumatoid arthritis since 1942.^[2]

Throughout the 1950s, Bruce studied sexual behaviour in laboratory mice, with a particular interest in oestrus synchronisation.^[2] In one experiment, she housed newly mated pregnant females with male mice that were not the father of the carried embryo. As a result, the rate of miscarriages increased, these females subsequently returning to oestrus and mating with the new male.^[5] No increased rate of miscarriages occurred when pregnant mice were paired with juvenile or castrated mice.^[6]

Her colleague Alan Parkes, who had recruited her to the NIMR in 1944,^[3] helped her to pursue the initial findings that eventually lead to this discovery.^[7]

Following the isolation of pure vitamin D in 1931, Bruce worked in collaboration with Askew, Philpot and Webster in the Department of Biological Standards, determining the stability of the pure substance.^[8] At this time, Bruce was also working with Dr Callow in the Department of Physiology, Pharmacology and Biochemistry, determining the healing effect of vitamin D in rats with rickets.^[9]

• Bourdillon, R. B.; Bruce, H. M. (1 January 1932). "The determination of vitamin D". Biochemical Journal. 26 (2): 506–521. doi:10.1042/bj0260506. PMC 1260932. PMID 16744851.
• Bruce, H. M. (1934). "Interaction of vitamin D and dietary factors in the healing of rickets in rats". Biochemical Journal. 28 (2): 512–516. doi:10.1042/bj0280512. PMC 1253223. PMID 16745413.
• Bruce, H. M.; Hindle, E. (July 1934). "The Golden Hamster, Cricetus (Mesocricetus) auratus Waterhouse. Notes on its Breeding and Growth". Proceedings of the Zoological Society of London. 104 (2): 361–366. doi:10.1111/j.1469-7998.1934.tb07757.x.
• Bruce, Hilda M. (1959). "An Exteroceptive Block to Pregnancy in the Mouse". Nature. 184 (4680): 105. doi:10.1038/184105a0. PMID 13805128.
• Bruce, H. M. (1965). "Effect of Castration on the Reproductive Pheromones of Male Mice". Reproduction. 10: 141–3. CiteSeerX 10.1.1.485.8060. doi:10.1530/jrf.0.0100141. PMID 14337805.