The spiky beasts have been moved to Bristol to avoid a cull, after they were accused of eating rare bird eggs.
Bristol University scientists hope to fit 46 more hedgehogs with transmitters to find out if relocating the hogs rather than killing them is possible.
Professor Stephen Harris said: "It's important to know how the released animals affect the wild hedgehogs."
The team will look at how many Uist hedgehogs survive, and how they get on with the local hogs.
The first four beasties were set loose into gardens across Bristol on Monday.
Hear story
Your e-mails about the hogs
Try our hedgehog quiz
It's wrong to kill hedgehogs
