The answer to this question is the grey short-tailed opossum.
How is this possible?
This unique ability is due to a phenomenon called delayed implantation. Here's how it works:
- Fertilization: The opossum ovulates and is fertilized.
- Delayed Implantation: The fertilized egg doesn't immediately implant in the uterine wall. Instead, it remains dormant for several weeks.
- Pregnancy: If the opossum becomes pregnant again during this dormant period, the second fertilized egg will implant and begin developing. This means the opossum can be pregnant with two litters at the same time, one in the early stages of development and the other already further along.
Why does this happen?
Delayed implantation is a survival strategy for opossums. It allows them to time their pregnancies with favorable conditions for raising their young.
Other animals with delayed implantation:
While the opossum is the only known mammal that can be pregnant with two litters simultaneously, several other animals also exhibit delayed implantation. These include:
- Bears
- Seals
- Weasels
- Badgers
This adaptation helps these animals synchronize their reproductive cycles with the availability of food and favorable environmental conditions.
