The moment a woman finds out she is pregnant can be life changing. But what about animals – do they know when they have a little one on the way? As it turns out, many animals do show signs that indicate they are aware of their pregnancy.

If you’re short on time, here’s a quick answer: Most mammals and some birds show behavioral and physical signs during gestation that suggest they have some level of awareness that they are pregnant.

Behavioral Changes in Pregnant Animals

Nesting Instincts and Protective Behaviors

When an animal becomes pregnant, one of the first behavioral changes noticed is an increase in nesting instincts. Dogs may burrow on blankets or search for a comfortable room in the house, while cats go on the hunt for a secure and secluded place to have their kittens.

According to the ASPCA, a pregnant cat’s nesting instinct emerges about a week before delivery as she looks for an out-of-the-way spot with warmth and safety.

Along with finding suitable dens or nests, pregnant mammals can become more protective due to hormonal changes. A 2013 study published in Animal Behaviour observed that pregnant mares were more likely to act aggressively toward unfamiliar horses in order to protect their future offspring.

Many cat owners also report increased aggression from the family feline in the later stages of pregnancy.

Changes in Appetite and Activity Levels

In the animal kingdom, pregnancy usually leads to extra hunger and weight gain as the mother nourishes her growing babies. According to the academian portal Classroom, a pregnant dog will need 25-50% more food than normal in the final third of gestation when puppies do most of their development.

Cats also tend to have heartier appetites and may beg more insistently for food.

While eating for two or more leads to an initial spike in appetite, activity levels tend to decrease by 15-20% in pregnant dogs and cats according to veterinarian Dr. Margareth Vogel in an interview with the website Rover.

These behavioral shifts help conserve the energy pregnant animals need for the demands of late pregnancy and birth. An expectant mother dog may spend more time napping while cats nestle in their new dens.

Physical Signs of Pregnancy in Animals

Weight Gain and Abdominal Swelling

One of the most obvious physical signs of pregnancy in animals is weight gain and abdominal swelling. As the fetus or fetuses grow inside the womb, the belly expands to accommodate them. The amount of weight gain and swelling varies by species.

For example, a pregnant dog may gain 15-25% more body weight while a mare (female horse) gain only 5-10%. Elephants, on the extreme end, can gain a whopping 200-600 pounds during gestation!

Abdominal swelling is generally more noticeable in slender animals like cats, dogs and rodents. In animals with barrel-shaped bodies like pigs, it can be harder to visually detect pregnant bellies. Palpation or ultrasound by a veterinarian is often required to confirm pregnancy in pigs.

An interesting exception is the pot-bellied pig, which has a swayed back and very obvious baby bump when expecting piglets.

Changes in Hormones and Body Temperature

Along with weight gain, pregnant animals experience fluctuations in hormones like progesterone, estrogen, and relaxin. These hormonal shifts lead to physical changes that indicate pregnancy. An easy one for pet owners to observe is nipple enlargement and reddening of the mammary glands in preparation for nursing.

This generally occurs in the second half of gestation in dogs and cats.

Changes in body temperature can also signify pregnancy in animals. Basal body temperature drops below normal levels at the time of conception and implantation of the embryo. It then rises and remains slightly elevated throughout the pregnancy term.

Horse owners and breeders commonly track body temperature changes to pinpoint the day of conception and projected due date.

More dramatic body temperature fluctuations happen right before labor begins. Pregnant mammals often experience a noticeable temperature drop 24-48 hours prior to giving birth. When a pregnant cat, for example, sees her temperature decline a degree or more, owners know kittens are imminent within the next day!

Can Animals Detect Pregnancy in Others?

It’s incredible, but research shows that yes, some animals have the remarkable ability to detect pregnancy in other members of their species. Dogs in particular have an uncanny talent thanks to their keen sense of smell.

Studies reveal dogs can identify human pregnancy as early as 3 weeks after conception by noticing subtle hormonal changes. Wildlife biologists have also observed peculiar pregnancy detection behaviors in elephants, deer, seals, and coyotes.

The Nose Knows: Dogs Sniffing Out Pregnancy

A dog’s nose is about 100,000 times more sensitive than a human’s. Their 300 million scent receptors allow them to pick up on incredibly faint smells we don’t notice. Numerous reports document dogs alerting their owners to an unexpected pregnancy by suddenly becoming overprotective, attentive, or drawn to the stomach area – sometimes long before the person even took a pregnancy test!

In 2013, researchers put dogs’ pregnancy detection skills to the test. Trained sniffer dogs were able to correctly identify which women were pregnant about 70% of the time just by smelling underarm sweat samples. An extremely impressive result!

Elephants Guarding Expectant Mothers

Elephants live in tight-knit matriarchal groups with deep social bonds. When a female elephant is pregnant, other members of the herd spring into protection mode. They often form a defensive circle around the pregnant mother and even help her roll on her side if she struggles to get up.

It’s speculated elephants know about pregnancy before any physical signs appear thanks to their intelligent and empathetic nature.

Deer Respecting Privacy for Fawns

Female deer usually give birth to fawns in secluded wooded areas away from the herd. Remarkably, other deer show understanding about the need for privacy during this time. Though normally highly social, the rest of the herd leaves the pregnant females alone for several weeks around the birthing period.

Biologists theorize deer can sense hormonal changes signaling pregnancy and keep their distance accordingly.

nature is incredible! Animals never cease to amaze with their extraordinary senses, intuition, and social intelligence. Clearly there’s still much to discover about the secrets of the animal kingdom!

Exceptions Where Animals May Not Know

While many animals do seem to recognize when they are pregnant, there are some exceptions where animals may not be aware of their expecting state:

Animals with Short Gestation Periods

Some animals like mice, rabbits, and hamsters have very short pregnancy lengths, often less than a month. Their rapid reproductive cycles and large litters likely mean being pregnant is almost a constant state.

With nearly back-to-back pregnancies, these species may lack strong biological cues to signal a new pregnancy.

Solitary Animals

Animals that lead mostly solitary lives, like snakes, lizards, and spiders, may not recognize pregnancy either. Without social structures or bonding behaviors, the biological changes of pregnancy may go unnoticed in isolation.

Aquatic Animals

Aquatic species like fish and sharks lack some of the most obvious physical signs of pregnancy that mammals and birds display. Weight gain and abdominal swelling are less pronounced underwater. And behaviors like nesting don’t apply. So pregnancy recognition may be muted for them.

Animals with Surprise Births

Some animals actually do appear oblivious to pregnancy until they give birth. Kangaroos and dolphins, for example, can seem unaware they are pregnant, going about normal activities until they suddenly produce offspring.

Their surprise births suggest they lacked strong internal cues of their pending deliveries.

So while many species demonstrate pregnancy-specific behaviors and changes, others seem truly unaware of their gravid state. For animals with short gestations, solitary lives, aquatic habitats, or surprise births, recognizing pregnancy may be muted or absent altogether.


While we can’t get inside the minds of animals, observational evidence suggests most mammals and some bird species do go through changes during gestation that indicate an awareness of their pregnant state.

From changes in hormones to behaviors preparing for offspring, pregnant animals seem to experience their own version of a nine month journey into parenthood.

The most obvious signs are preparation of dens and nests, while more subtle cues from changes in body chemistry probably also play a role. So while we may lack a definitive answer, the evidence points to pregnancy being an exceptional time even in the animal kingdom.

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