Bears usually live alone, except when they are mating season.

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Is this sentence grammatical? Correct errors, please.

Bears usually live alone, except when it is mating season.

Thank you. What about the following?

1. Bears usually live alone, except when they have a mating season.
2. Bears usually live alone, except when they have mating seasons.
3. Bears usually live alone, except when they have mating season.

All of those three are incorrect. Sorry.

Correct expressions......(have a mating season/have mating seasons)

1. Why don’t humans have a mating season? (BBC)

2. What animals have mating seasons?
Some animals that are long-day breeders include ring-tailed lemurs, horses, hamsters, groundhogs, and mink. "Short-day" breeders cycle when the length of daylight shortens (fall) and are in anestrus in spring and summer.

3. During the mating season, schools of passionate cod make so much noise that the submarine's sonar cannot hear anything else.

More example sentences

1. Males are usually solitary except during the mating season.
2. The sea turtles reach the shore during their mating season, December-January.
3. Adult males advertise the most, especially in the mating season.
4. We studied red-sided gartersnakes in central Manitoba, Canada during their mating seasons in May 1997 and May 1998.
5. During mating season, males fly over their territories piping clear, melodious notes.
6. Males in better condition at the start of the mating season will be more successful.
7. Males sing to attract mates, and once paired, they continue to sing throughout the mating season.
8. Males and females only get together during mating season.

9. The pandas only have one mating season per year.

10. It was just over one hundred days to the elephant mating season.
11. In mating season, the male sings deliriously as he whirrs madly over the hayfields.

Yes, the sentence is grammatically correct. However, it can be improved by adding a few articles. Here's the corrected version:

"Bears usually live alone, except during the mating season."