Does your dog know when a family member is pregnant?

A woman, who had been a former student in our dog obedience club, stood beside a large mixed-breed dog and spoke to me in a worried tone. “I don’t know what’s wrong with Max.

You know that he was always such an easy-going dog, but now, when we go out on walks, he barks or threatens other dogs that we meet and even some people that we meet. Can you tell me what’s wrong with him?”

I looked at her and noticed a pronounced baby bump, which seemed to indicate that she was about six months pregnant, and I thought I knew the answer.

There are many anecdotal reports of noticeable behaviour changes in dogs when a family member becomes pregnant. The two ends of the reported behavioural spectrum range from a clingy, over-affectionate set of behaviours to a much more reactive, defensive set of behaviours.

One dog trainer I know told me that whenever there are sudden behaviour alterations in a dog, trending toward either of these extremes, the first thing she asks her clients is if they know whether they are pregnant or think they might be pregnant. Her response is based on casual observations and reports from her students and other trainers, but now there is scientific data.

A Scientific Test of Anecdotal Reports

Sarah Wilson of the School of Biological Sciences at Queen’s University Belfast in Northern Ireland and her team of researchers decided to scientifically test whether dog behaviours changed when someone in the household became pregnant. The team obtained data from 130 individuals who owned a dog during a pregnancy.

These investigators used a broad online survey in which the dog owners were asked to report on specific aspects of their dog’s behaviour before and during the time that they became pregnant. Information was gathered about five different categories of their dogs’ behaviour during that time.. The first of these involved attention-seeking (which included increased cuddling, sniffing, or nuzzling).

The remaining four groups of behaviours that they assessed all have very similar content. The first was guarding or protective behaviours while in the presence of familiar people (such as growling or lunging at them), and the same questions about protective behaviours were asked for the situation when the dog was in the presence of unfamiliar people. The investigators labelled the last two groups of behaviours as “fearful” or “anxious” behaviours. One set involved what happened when the pet dog was in the presence of another dog. The list of behaviours covered here was very similar to the guarding behaviours and included additional items to assess agitation and restlessness. Finally, they asked the same set of behaviours targeting the pregnant woman herself.

Does the Dog’s Behaviour Change Around a Pregnant Woman?

Given the number of different measures, the research team applied high-powered statistical analyses; however, the results were very straightforward. This scientific and quantitative investigation confirmed the conclusions suggested by the anecdotal evidence. Nearly two-thirds of the participants (65.4 percent) reported that they believed their dog’s behaviour changed when they became pregnant. The analysis showed a marked increase in attention-seeking and affectionate behaviours.

At the other end of the behaviour range, there was also a noticeable increase in protective and guarding behaviour around familiar and unfamiliar people. There was also an increase in similar behaviours and agitation when the pet dog associated with other dogs (whether familiar or unfamiliar). Finally, no such negative behaviours targeted the pregnant individual herself.

How Soon Does a Dog Know Someone Is Pregnant?

One of the surprises that emerged from this study is that more than a quarter (26.9 percent) of the participants reported that they believed that their dogs’ behaviour changed before they were aware they were pregnant.

Perhaps this finding should not be so surprising because there are huge hormonal shifts that occur after impregnation. For example, human chorionic gonadotropin hormone (hCG) is only produced during pregnancy. It is well known that dogs are highly sensitive and can detect changes in bodily scent produced by hormones.

Other hormones can cause behaviour changes in women and emotional shifts that dogs may be able to detect. For example, fatigue and moodiness can increase as estrogen and progesterone levels rise. This can cause adjustments in a female that may result in fewer walks, fewer play sessions, and increased irritability that the dog can certainly detect and respond to.

If you are a biological female, and your pet dog has shown a sudden behaviour change (ranging from increased clinginess to increased protectiveness), it might be wise to check a home pregnancy test — you might just find that it registers two lines!