When Love Is in the Air: Understanding Why Dogs Tend to Mate when It Rains - PubMed (original) (raw)

When Love Is in the Air: Understanding Why Dogs Tend to Mate when It Rains

Sreejani Sen Majumder et al. PLoS One. 2015.

Abstract

Seasonality of reproduction is observed in many species of organisms, across taxa, and is influenced by both biotic and abiotic factors. While such seasonality is easy to understand in temperate species exposed to extreme climates, it is more difficult to explain in the tropics. In many tropical species offspring are born during the season of high precipitation, which also coincides with high resource availability. Interestingly, in India, free-ranging dogs seem to mate, and not whelp, when it rains--an observation that cannot be explained by the resource abundance hypothesis. We carried out an extensive study to identify the mating seasons of free-ranging dogs, and observed a strong correlation between both the incidence and frequency of mating related behaviours of dogs, and precipitation levels. There are two clear mating seasons, of which the primary mating season coincides with the monsoon (rainy season) and the secondary mating season coincides with the nor'westerlies in this part of India. We speculate that this strong correlation is an effect of chemistry, rather than biology. While male dogs can mate round the year, females come into estrous seasonally. In the urban environment, dogs are exposed to a lot of olfactory noise, which can dilute the signal present in sex pheromones of the females in heat. A shower leads to increased humidity and reduced temperature of the air, leading to intensification of pheromone signals that trigger a sexual response in the dogs.

PubMed Disclaimer

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1

Fig 1. The occurrence of mating related behaviours (MRB) was highly correlated with precipitation levels (mm).

The precipitation levels reported here are actual readings of precipitation on the day of observations, as given by IMD. The linear fit is given by the black line, represented by the equation y = 0.4888x + 18.893, R2 = 0.6117.

Fig 2

Fig 2. The frequency of MRB varied with precipitation levels.

The bar chart shows the mean and standard deviation of the frequency of all MRB occurring at different levels of precipitation (as noted during the time of observations), over four years, 2010 to 2013, during the primary mating season. Variation in the frequency of MRB was not significant across the four years within a precipitation category (alphabets), but varied significantly different levels of precipitation within a year (*).

Fig 3

Fig 3. All MRB showed variation across precipitation categories.

Mean and standard deviation of the frequency of different mating related behaviours observed at the three precipitation levels noted during the time of observations—the different alphabets represent significant differences within a behaviour category, between precipitation levels.

Fig 4

Fig 4. The year-long census showed that highest MRB occur in the monsoon.

A bar chart showing the mean and standard deviation of the frequency of MRB per location in the four seasons. Different alphabets represent significant differences in the frequency of MRB between seasons. 40 locations were used in the study.

Fig 5

Fig 5. The frequency of MRB per location increased with increased precipitation.

A scatterplot showing the significant interaction between the numbers of MRB observed per location at different levels of precipitation (as recorded from IMD). The dotted line shows the linear fit, and is represented by the equation y = 0.1243x + 0.581, R2 = 0.4704.

Fig 6

Fig 6. MRB and precipitation patterns show convergent double binomial trends.

The plot shows the relationship between the occurrence of mating related behaviours (MRB) and precipitation levels over a year, on a fortnightly basis. The red dots represent the number of MRB averaged over the number of locations sampled in a fortnight and blue dots represent the average precipitation level (from IMD) considering only the days of the census. Both the datasets fit double normal distributions, as represented by the lines of the respective colours. A1 and A2 represent the two amplitudes of the respective curves at x0 time as read from the x-axis.

Similar articles

Cited by

References

    1. Bronson FH. Mammalian reproductive biology, pp. 51–52 Chicago, IL: The University of Chicago Press; 1989.
    1. Bronson FH, Heideman PD. Seasonal regulation of reproduction in mammals In The physiology of reproduction (eds Knobil E., Neill J. D.), 2nd edn New York, NY: Raven Press; 1994.
    1. Prendergast B. Internalization of seasonal time. Horm Behav. 2005; 48: 503–511. - PubMed
    1. Bronson FH. Seasonal variation in human reproduction: environmental factors. Quart. Rev. Biol. 1995; 70: 141–164. - PubMed
    1. Brockman DK, van Schaik CP. Seasonality in primates: Studies of living and extinct human and non-human primates. Cambridge University Press; 2005.

Publication types

MeSH terms

Grants and funding

The work was funded by the Women's Excellence Award No. SB/WEA-005/2013 by the Science and Engineering Board, Department of Science and Technology, India to AB; Indian Institute of Science Education and Research Kolkata, India provided infrastructural support.

LinkOut - more resources