Someone needs to check the manual - Page 1

This question is mainly towards people who have bred dogs and work with breeding stock. I have a 13 month old, intact male GSD. He lives with two spayed older females, my other GSD who is 3 and a 10 year old lab bitch. The lab bitch is a retired brood bitch. She had a total of 3 litters of puppies in her career and has been spayed since 2008. She's not particularly dominant, has never been aggressive about food or resources and she and my GSD bitch get along like gangbusters. Now the young male isn't particularly randy, no more or less than any other young male, he's gotten a little sexual in his play with the GSD bitch but she just warns him off, no big deal. He's NEVER tried to mount or play with the lab bitch. Recently, in the past month the lab bitch has started to get extremely aggressive in mounting HIM however. If he's out of the crate and she sees him, she runs over and jumps on him and just starts to go to town. Honestly, have to admire her technique, were she a breeding male, she'd be the classic Wham Bam thank you ma'am and she practically needs a step stool to reach him but it doesn't slow her down. Needless to say, he tries to just 'walk out of it' but she'll have a vice grip on him. He'll turn and grumble at her to GTFO but she's busy and usually we have to grab her and tug her off him. She only does this with him, not with the female and never with any other dog she's interacted with over the past 2 years we've owned her. Any idea what's got her going in this case? It was amusing at first (and ... well still is) but it really needs to stop.

Dominance

What Phil said. Prison rules

She's lived with him since February.  Any thoughts on why she's suddenly amped up in the past 4 weeks?

He's getting older

I hate hormones.