Baby Calendar
Hoping For Your New Short-Tailed Opossum Litter
By Molly Kalafut
This is a calendar provided to help determine when your short-tailed opossum litter might be born, and when to start over if the mating wasn't successful.
General Counting Principles
Gestation takes 14 days *after a successful mating*. When the pair is placed together, most short-tailed opossums successfully mate around day 7, and the young are born 14 days later, so - most litters are born exactly 21 days after the female is first paired with the male. Very rarely, a successful mating might occur on Day 1, and since gestation takes 14 days the litter might be born 15 days after the female is first paired with the male.
Most breeders don't witness the actual mating, which is why keeping track of when the pair were placed together and separated is important. Also, since the female sometimes becomes more aggressive to the male after a successful mating (usually around Day 9 or after), it is important to know when they were placed together to make sure the male is removed.
How To Use The Calendar:
Start counting with the first day the STO are paired together, and on the calendar then mark the day the male is removed (usually between days 9 and 12). If you witness successful mating, where the male wrestles the female down and 'ties' with her, mark that date on the calendar too.
Calculating Litter Date If Mating Is Observed: If you witnessed the mating event, the litter should be born 14 days later.
Calculating Litter Date if Mating Is Not Observed: If the mating was successful (but you didn't see it), Day 21 is the day most likely for a litter, but it may happen before or after depending on the day the mating occurred.
Calculating The Last Possible Day For A Litter: Start at the date the male was REMOVED from the female's cage. Add 15 days. Circle that date. For Example: If the male is removed on Day 10, then the last possible day they could have a litter is Day 25. If the male is removed on Day 12, the last possible day they could have a litter is Day 23
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Short-Tailed Opossum Litter Calendar |
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| Week 1: Introduction Mating |
Day 1 Male & Female placed together |
Day 2 |
Day 3 |
Day 4 |
Day 5 |
Day 6 |
Day 7 Day most likely for mating |
| Week 2: Mating Separation |
Day 8 |
Day 9 |
Day 10 |
Day 11 |
Day 12 Remove Male* |
Day 13 | Day 14 |
| Week 3: Gestation Birth |
Day 15 Litter is possible (though unlikely) |
Day 16 | Day 17 | Day 18 | Day 19 | Day 20 | Day 21 - Litter will most likely be born |
| Week 4 Birth or Bust! |
Day 22 | Day 23 | Day 24 | Day 25 | Day 26 | Day 27 | Day 28 If no litter, time to start over |
* Remove the male by Day 12, if you haven't already. Most breeders remove the male between days 9 and 12.
