As mentioned a few months ago, I found a ranch with addax/scimitar oryx crosses and am currently trying to secure a hunt. When researching I ran across this internet info as other animals that would produce hybrids:

The listed hybrids include: Bongo/Sitatunga; Lesser Kudu/Sitatunga; Eland/Greater Kudu; Blue Duiker/Maxwell's Duiker; Bay Duiker/Red-flanked Duiker; Bay Duiker/ Zebra Duiker; Black Duiker/Kaffir Duiker; Cape Hartebeest/Blesbok; Bontebok/Blesbok; Black Wildebeest/Blue Wildebeest; Common Waterbuck/Defassa Waterbuck; Defassa Waterbuck/Nile Lechwe; Defassa Waterbuck/Kob; Nile Lechwe/Kob; Kafue Lechwe/Ellipsen Waterbuck; Red-fronted Gazelle/Thomson's Gazelle; Beisa Oryx/Fringe-eared Oryx; Grant's Gazelle/Thomson's Gazelle; Beisa Oryx/Gemsbok; Arabian Oryx/Scimitar-horned Oryx; Thomson's Gazelle/Roosevelt's Gazelle; Slender-horned Gazelle/Persian Goitered Gazelle; Persian Gazelle/Blackbuck; Cuvier's Gazelle/Slender-horned Gazelle. Oryxes and Addaxes freely interbreed, forming fertile hybrids, and Berlin Tierpark had a triple hybrid when a female (Addax x Scimitar-horned Oryx) was bred to a male Arabian Oryx. Addax/Oryx hybrids closely resemble the Addax parent and are sometimes erroneously traded as Addax; when the hybrids are bred back to the parental species of Oryx, the second generation more closely resembles the Oryx. This readiness to interbreed has implications for conservation with some zoos discovering their Oryx stock to be mongrelised.

Of course we know sika and elk will cross and there are whitetails and mule deer crosses also. My favorite is the gemsbok/scimitar cross !

I know this is going to be viewed as a stupid question, but I really would like to know. When an elk (fairly large animal) and a sika (not so large) breed, how the heck does it happen? Is this only done artificially? Is it always male of one species female of the other? Would a sika be able to breed a red deer? Just one of those things I have wondered. I like to assume it is always one super sika bull just fearlessly wondering up to a lonely cow elk and given her the "how you doin'?" Then after they find a nice stump for the little guy to balance on the rest is history

I don't know the ins and outs of what happens with a sika and an elk, but I sure have seen a lot of them that look like a sika with massive antlers and outfitters claiming them to be 100% sika.

Have you ever heard of John Holmes? Some animals are very well endowed.

Ireland and Scotland have problems with Red Deer and Sika interbreeding. The Silk Deer or Sika Grande is an AI cross between Elk and Sika. In the wild, the size differential tends to keep Ska and Elk apart, but with the larger Manchurian and Dybowski lines, it's possible that a yearling elk could breed a hind. In Scotland, the've found that there isn't much of a problem when there are good populations of both, but where populations are marginal there can be a lot of cross species breeding.

I'm not a fan of the crossbreeding of the African game species.

I've seen what happens when a Santa Gertrudis bull impregnated a Hereford cow. Calf had to be sawed in 3 pieces to be removed after it got stuck on the way out. Cow died just as Doc was stitching her up.

After thinking about it it's more likely that a Dybowski Stag could impregnate a yearling Elk cow than the other way around. It also bears noting that the problems in Scotland come a least partially from the fact that the Scottish Red Deer is one of the smaller races of Red Deer. The Silk Deer(elk x sika) was an attempt to get a more manageable size animal for venison farming.

Always thought Sika and Elk cross were called Silk, while a Sika and Red Stag cross was referred to as Sika Grande?

All About Exotics used both to refer to Sika/Elk cross but you may be correct. http://www.allaboutexotics.com/exotic-species/texas-silk/