The relationship between infanticide and pregnancy block in mice

Area of Science:

• Reproductive behavior
• Behavioral ecology
• Animal behavior

Background:

• Pregnancy block, also known as the Bruce effect, is a biological phenomenon where a pregnant female mouse loses her pregnancy upon exposure to a novel male.
• Infanticide, the killing of young by adult conspecifics, is a reproductive strategy observed in various species, including rodents.

Purpose of the Study:

• To investigate whether newly pregnant mice can assess the risk posed by infanticidal males and adjust their reproductive tactics accordingly.
• To determine the adaptive advantage of pregnancy block in the presence of males exhibiting infanticidal behavior.

Main Methods:

• Newly pregnant mice were exposed to either infanticidal or noninfanticidal males.
• Pregnancy block incidence was recorded.
• Pup survival rates were compared between groups exposed to different male types.

Main Results:

• Females exposed to infanticidal males were more likely to exhibit pregnancy block compared to those exposed to noninfanticidal males.
• Females that did not exhibit pregnancy block in the presence of infanticidal males experienced a greater loss of pups.
• No difference in pregnancy block was observed when females were served by infanticidal or noninfanticidal males, but pup loss was higher if litters were produced by infanticidal males.

Conclusions:

• Female mice demonstrate the ability to assess potential threats to their offspring and modify their reproductive strategies, such as implementing pregnancy block.
• Pregnancy block serves as an adaptive mechanism to mitigate the risk of infanticide and maximize reproductive success in hazardous social environments.