Timing of reproduction and association with environmental factors in female free-roaming dogs in southern India

•Pregnancies in free-roaming dogs were concentrated seasonally.•Decreasing daylength was statistically-significantly associated with more pregnancies in free-roaming dogs in Goa.•Temperature change was statistically-significantly associated with pregnancies in dogs in the Nilgiris.•The relationship between temporal and environmental factors and pregnancies in free-roaming dogs varied with location. Annual peaks in reproductive activity have been identified in multiple domestic dog populations. However, there is little evidence to describe how these peaks may be associated with environmental factors such as daylength, which plays a well-established role in breeding patterns of seasonally-reproductive species. Data were collected 2016–2020 during 7,743 and 4,681 neuter surgeries on adult female unowned free-roaming dogs in veterinary clinics in Goa and Tamil Nadu respectively. Temperature, precipitation, relative humidity, and daylength data were gathered for time periods preceding the neuter surgery that may have influenced the likelihood of pregnancy (potential influence periods). A multivariable generalised additive model was used to assess the relationship between these factors and pregnancy. The prevalence of pregnancy varied by month in both locations indicating seasonality of reproduction in these groups. The annual pattern was more distinct in Goa with a peak in pregnancies between September and December. In Goa, decreasing daylength was associated with a higher probability of pregnancy (p = 0.040). Decreasing temperature was associated with decreasing probability of pregnancy in the Nilgiris (p = 0.034). Bitches had a median of 6 foetuses, with no evidence of seasonal variation. Environmental factors were associated with patterns of pregnancy in free-roaming dogs, however statistically-significant factors varied by geographical location. Establishing local seasonal patterns of breeding in free-roaming dogs and assessing their relationship with environmental influences is recommended to facilitate effective and efficient population management strategies, which aim to reduce conflict between human and free-roaming dog populations.