Certain animals, like humans, possess the remarkable ability to develop their offspring within their placenta. The placenta, an organ that plays a crucial role in gestation, facilitates a multitude of functions, including the transfer of oxygen, nutrients, and other beneficial substances from the mother to the developing fetus. Many examples of placental mammals, also called eutherians, have longer gestations and give birth to young that are relatively developed compared to marsupials and monotremes.
Additionally, these animals have a wider opening at the base of the pelvis, which enables the birth of a large baby in comparison to the mother’s size. In this article, we’ll explore several mammals that possess this remarkable adaptation and delve into the details of their reproduction process.
13 Examples of placental mammals
1. Black rhinoceros
Scientific Name: Diceros bicornis
One of the largest placental mammals that you’ll encounter in Africa is the black rhinoceros. They extend their range from Cameroon to South Africa, frequently inhabiting diverse habitats such as grasslands, deserts, and tropical forests, where they can find water sources within a distance of 25 kilometers.
They display solitary behavior and engage in a polygynous mating system, wherein they mate with multiple females. A single calf is born to female Black rhinos after a development period of 15 to 16 months of development. The mother rhino then takes on the responsibility of nurturing and protecting her offspring for a duration of up to four years.
2. Four-toed hedgehog
Scientific Name: Atelerix albiventris
The Four-toed hedgehog is a creature that has a remarkable skill – they can curl themselves into a defensive ball and raise their quills as a means of protection when faced with danger. These hedgehogs breed once or twice a year, engaging in mating activities during the rainy and warm seasons when food is abundant.
This mating behavior typically occurs between the months of October and March. The spiny offspring are born after a gestation period of 35 days, and they usually give birth to around 6 offspring, which mature at about two months of age.
3. Star-nosed mole
Scientific Name: Condylura cristata
One of the eutherians you may encounter in North America is the star-nosed mole that thrives in moist habitats with poor drainage, including forests, wet meadows, and marshes. During the breeding season, this species engages in monogamous behavior, forming pairs as early as autumn, and mates during the months of March and April. After a 45-day gestation, females give birth to 2-7 hairless offspring that become independent at 30 days and mature at 10 months.
4. African bush elephant
Scientific Name: Loxodonta africana
Among the well-known mammals that roam the continent of Africa are African elephants. These large animals have a polygynandrous mating system, meaning they engage in multiple mating with different partners.
They do year-round breeding, with a development period lasting 22 months, and give birth to calves weighing between 198 and 265 lbs. These newborns depend on their mother’s milk for 4 months. Around 8 years of age, these young animals achieve full independence, with males reaching maturity at 20 years and females at 11 years.
Scientific Name: Panthera leo
The Lions are large carnivorous mammals you’ll find in savanna habitats. These skilled hunters frequently target ungulates as prey and reproduce year-round, primarily through polygynous mating.
Lionesses deliver their cubs after a gestation period of 3.5 months. These cubs are then nurtured and cared for by the lionesses until they gain independence at around 16 months of age.
Scientific Name: Pan troglodytes
Many placental mammals inhabit the central African tropical forests, including the chimpanzees. Chimpanzees engage in complex reproductive behaviors, as both males and females seek out multiple partners for mating.
They have a gestation period of about 202 to 260 days, during which typically only one young is born. You’ll see mothers carrying their babies on their backs for three to six months until the babies stop weaning at three to four years old.
7. Brown bear
Scientific Name: Ursus arctos
Brown bears have a vast habitat range that spans from desert fringes to mountainous forests. In North America, tundras, alpine meadows, and coastlines are where you’ll find them. While females are smaller, males can grow to a height of 8 feet and a weight of over 1700 lbs.
Their mating season is between May and July, during which time a delayed implantation occurs in the uterus five months after the mating process has taken place. The following development period will last 6 to 8 weeks, making the entire pregnancy last 180 to 266 days (including pre-implantation).
8. Pygmy three-toed sloth
Scientific Name: Bradypus pygmaeus
The Pygmy three-toed sloth is an eutherian that exclusively inhabits the coastal red mangroves along the coast of Panama. They have an arboreal behavior, remaining active throughout the day.
As solitary creatures, their mating behavior isn’t fully understood, but male competition for receptive females is observed in them. Breeding occurs during the dry and wet seasons, with births taking place after a 6-month gestation, aligning with periods of abundant food.
9. Jamaican fruit bats
Scientific Name: Artibeus jamaicensis
Bats are the only placenta mammals that can fly, and the Jamaican fruit bat is one of the ones you can find in Central and Northern South America. You can see this flying mammal living in a variety of habitats, including plantations, dry forests, and rainforests.
The breeding of these bats generally coincides with the availability of food and the coming of the wet and dry seasons. Females deliver only one pup, although twins may be born on rare occasions.
Scientific Name: Canis lupus familiaris
Dogs are diverse domesticated offspring of gray wolves that have been bred for various purposes. Humans often control their breeding as they keep them as pets, making them one of the most popular animals.
The gestation period of these creatures spans 9 weeks, during which they give birth to litters consisting of 3 to 9 puppies. Dogs take part in cooperative care of their offspring, either with the assistance of other members of their social group or solely with their mothers, until the puppies reach the age of 8 to 10 weeks.
11. Nine-banded armadillo
Scientific Name: Dasypus novemcinctus
Another eutherian you can find in the Americas is the nine-banded armadillos. During the summer, these solitary creatures form pairs and partake in various behaviors such as touching, wagging their tails, and sniffing.
The reproduction of these animals also includes the process of delayed implantation, which leads to the birth of identical quadruplets in spring after a gestation period of four months. Young are born with advanced functionality, but it takes them several weeks to develop a hardened armor.
Scientific Name: Equus caballus
Horses, known for their large size and their remarkable ability to assist humans with transportation and labor, are among the domesticated placental mammals that one can easily identify. Horses undergo a development period of 335 days, during which they develop and nurture a single foal each year.
Foals can stand and walk within hours after birth, and they can start eating solid food within a week of being born. Domesticated horses typically undergo the weaning process at the age of four to six months, whereas wild foals require a longer period of up to two years.
Scientific Name: Tursiops truncatus
Dolphins are streamlined marine mammals that are placental and have a unique physiology. These creatures possess a unique characteristic that sets them apart from other underwater creatures: they use their mammary glands to nurse and nourish their calves.
Polygamous mating is also a part of their breeding process, wherein they engage in multiple partners. The gestation period lasts approximately 12 months, resulting in the birth of a single calf. Females nurture their young for a duration of 18-20 months, and they only breed every 3-6 years.
- “What is a placental mammal anyway?”, J. A. Capra, P. Abbot, National Library of Medicine, September 12, 2017, ncbi.nlm.nih.gov