Litter size, the number of offspring a mammal gives birth to at once, varies dramatically across the class Mammalia. While large mammals like elephants and whales typically produce a single young, others deliver multiple offspring in a single birthing event. This strategy ranges from two or three young to dozens, reflecting diverse evolutionary adaptations across different ecological niches.
The Mammal with the Largest Litter Size
The record holder for the largest recorded mammalian litter size is the common tenrec (Tenrec ecaudatus). This small, spiny mammal is native to Madagascar and nearby islands. A female common tenrec can give birth to as many as 32 young in a single litter, far exceeding any other mammal species. Their average litter size is typically between 15 and 20 offspring.
This high fecundity is supported by a unique physical trait: the female tenrec possesses up to 29 teats, the highest number found in any mammal. The common tenrec resembles a hedgehog or opossum, growing 26 to 39 centimeters long and weighing up to 2.5 kilograms. After a gestation period of 56 to 64 days, the young are born during the wet, resource-rich months. This timing allows the mother access to the food needed to sustain her large litter.
Biological Drivers of Large Litters
The ability of the common tenrec and other small mammals to produce such large litters is connected to a life history strategy that favors quantity over extensive parental investment in each individual offspring. This approach is often seen in species with short lifespans and high mortality rates, particularly among the young. These mammals invest their energy into producing many small, relatively underdeveloped neonates, hoping that a few will survive to adulthood.
This strategy is driven by the high rate of predation faced by both parents and young. For species that conceal their young in burrows or nests, like the tenrec, maximizing the number of offspring offsets inevitable losses. Environmental factors, such as resource availability and seasonality, also influence litter size. Maximal numbers are often observed in seasonal regions when resources are abundant.
Smaller body size is correlated with larger litters because smaller females have lower energy demands and can allocate a greater proportion of resources to reproduction. The common tenrec is an insectivore, and its energy-rich, invertebrate-based diet fuels its reproductive output. Tenrec offspring reach sexual maturity in a matter of weeks, increasing the potential for a high population growth rate.
Other Notable High-Volume Mammals
While the common tenrec holds the maximum species record, many other smaller mammals also produce substantial litters. The naked mole-rat (Heterocephalus glaber) is a contender, with one recorded litter reaching 33 young. Opossums, the only marsupials found in North America, can have litters containing up to 13 young.
Rodents are known for high reproductive capacity; domestic mice typically give birth to litters of 10 to 12 pups. Domestic pigs are another example, where selective breeding has led to an average litter size of 10 to 14 piglets. These high-volume births are a common pattern in small mammals, where a fast reproductive tempo is necessary for survival under high ecological pressures.