mammal reproduction

Internal fertilization

All mammals reproduce sexually by way of internal fertilization.

Monotremes

Monotremes have true mammary glands but lack nipples.

Marsupials

Marsupials produce an inefficient placenta, leading to short gestation time, birth of altricial young, and a long period of development in the pouch.

Eutherian mammals

Eutherian (placental) mammals have a highly sophisticated placenta supporting a longer gestation time and shorter nursing time relative to marsupials.

Testes functions

Tests produce sperm and synthesize testosterone.

Testes migration

In many rodents and some bats, the testes migrate from the body cavity into the scrotum during the breeding season and afterward are withdrawn afterward.

Permanent testes

In most primates, cetartiodactyls, perissodactyls, and carnivores the tests remain in the scrotum permanently.

Testes location in monotremes

In monotremes, anteaters, tree sloths, armadillos, manatees, dugongs, and seals (with some exceptions) the testes remain within the abdominal cavity.

Copulatory plugs

Copulatory plugs have been noted in many species of rodents and in some bats, insectivores, and marsupials.

Baculum

In all carnivores, most primates, rodents, bats, and some insectivores, the glans penis may include a bony structure known as the baculum that can be used to help identify species.

Corpora lutea

The number of corpora lutea is related to the number of ova produced, which can be used to evaluate the number of embryos potentially produced.

False pregnancy

A false pregnancy occurs when a corpus luteum is unfertilized yet maintained beyond the time of normal regression.

Estrus

In non-primates, a period of brief receptivity by females shortly before and after ovulation is known as estrus or heat.

Spontaneous ovulation

In the majority of mammals, ovulation is spontaneous, meaning it occurs without copulation.

Induced ovulation

Induced ovulation occurs when release of the ovum is triggered by the act of copulation in some mammals or the occurrence of green vegetation and associated nutritional factors in the diet of others (e.g., desert rodents).

Estrous cycle

During the breeding season, the time span from one period of estrus to the next is called the estrous cycle.

Monestrous vs Polyestrous

Monestrous species have one estrous cycle within a year, while polyestrous species have several estrous cycles within a year.

Post-birth ovulation

Many members of the rodent family Cricetidae (hamsters, voles, lemmings, muskrats, New World rats, and mice) are known to ovulate within an hour after giving birth.

Implantation

the attachment of the embryo to the uterine wall.

Functions of the placenta

physically anchoring the fetus to the uterus, transporting nutrients from mother to fetus, excreting fetal metabolites into the maternal compartment, and producing hormones that regulate mother and fetal organs.

Immune response in placental mammals

In placental mammals, the mother's immune response is suppressed so her body does not mount an attack against the otherwise alien placenta and embryo.

Deciduous placenta

A type of placenta associated with the portion of the uterus wall being torn away, with subsequent bleeding, when the placenta separates at delivery.

Placental scar

The pigmented area on the uterine wall that evidences the previous site of attachment of the fetus.

Nulliparous individual

An individual that has never given birth.

Parous

An individual that has given birth once.

Multiparous

An individual that has given birth more than once

Gestation

The period of time from fertilization until the birth of the young.

Delayed fertilization

A reproductive strategy most common in temperate bat species that undergo hibernation, with copulation occurring pre-hibernation.

Delayed development

A reproductive strategy where the blastocyst floats in suspended animation until environmental conditions favor further development.

Delayed implantation

A reproductive strategy where the blastocyst implants into the uterine wall after a period of suspended animation.

Altricial young

Young that are born hairless, blind, and essentially helpless.

Lactation

The production of milk by the mammary glands, a defining characteristic of Class Mammalia.

Colostrum

The first product released by the mammary gland following birth, a protein-rich fluid containing antibodies.

High-fat, high-protein milk

Milk produced by mothers of young mammals in northern environments to help them gain weight rapidly.

Teats

Structures in female mammals, except monotremes, that facilitate the transfer of milk to the young.

Mammary glands

Glands in female mammals that produce milk, the number of which tends to correlate with typical litter size.