Hybrid Vigor

Hybrid vigor is a principle of animal breeding which states that when animals of two different breeds are crossed, the resulting offspring will be larger and more vigorous than the purebred offspring of either parent breed.

Prime example:


“You’re not going to snatch me, are you?”

I’m don’t think I could snatch Bran anymore even if I wanted to. At three weeks he’s close to the size last year’s lambs were at two months. I don’t have any first-hand experience with newborn Shetlands, but I’m pretty sure they’re not usually this big.

Apart from his size, he looks like a purebred Soay at first glace. He definitely has some Shetland traits, though. I remember when I first saw him, the first thing I noticed was that he had Shetland eyes. Actually, the first thing I noticed was that he wasn’t white, and the second thing was that he was huge. His Shetland eyes were the first detail I noticed. His eyes are rounder and less slanted than Soay eyes; his head is also broader, and his nose is shorter than the Soay babies. I’m not sure if his stocky build and thick legs are a Shetland thing or another result of hybrid vigor.

The only thing that’s odd about him is his horns. All my other sheep have sharp-tipped horns, but the tips of his horns are rounded and lumpy, like he’s got safety nubs on them or something.


I’ve never seen horns like that before. The normal-looking section is new growth; the lumps at the tips were there when he was born. Probably just as well he didn’t have sharp little points on his head inside Princess. I’ve never had a lamb with that much visible horn at birth. Neo and Will were born with tiny buds just starting to come through, and Nova’s horns were just lumps under the skin when she was born.

He has a mostly Soay color pattern, but the base color of his wool I think may have come from his Shetland paternal grandmother. He looks brown in pictures, but he’s actually almost black. I don’t think he could have gotten that color from Princess, but Liam’s mother was a dark brown-black. It’s a bit early to speculate on his wool type, especially since I haven’t had a close-up look at Liam’s wool yet, but he definitely doesn’t have a Soay fleece. Soay lambs are born with a wavy, flat coat.


Will’s coat.


Mira’s coat.

Bran, however, is covered in tight little ringlets.


“Aren’t I a handsome boy?”

Very handsome. I’m very pleased with the cross so far. I’ll be happy to have another example for comparison, if Nova will ever get around to having her baby.


9 thoughts on “Hybrid Vigor

  1. Bran is such a cutie!! Love his nubby horns and little ringlets. I wonder if as he matures the ringlets will too–long, fluffy ringlets!!

  2. This is my first year lambing Shetlands and have just started looking into the history of the breed and have found that they were developed from a cross of viking sheep with Soays. The cross between them is fascinating and I look forward to following along in thier growth. Love Mira!

  3. Hi Sarah! I’ve got a week’s worth to catch up on . . . I love how I always learn something new from nearly all of your posts. I love the “safety nubs” on Bran’s horns! Which makes me wonder: do shepherds ever put “tips” on sharp sheep horns? I remember several months ago reading a blog where one Jacob’s sharp horns were causing all kinds of problems, but I don’t remember which blog it was!

    • I’ve never heard of putting something over the tips of horns, but I have heard of shepherds removing part or all of the horns from the occasional animal that likes to use the tips.
      Normal fighting by sheep with normal horns involves bashing with the forehead, so the tips aren’t really brought into play.

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