What is a "jumping trojan"? And what do their orbits look like? I was googling Neptune's trojan companions and found on Wiki this claim about  ~200 km diameter (316179) 2010 EN65:


  " the object is actually a jumping trojan, is jumping from the
  Lagrangian point L4 into L5 via L3."


So some asteroids not only oscillate between L4 and L5, between being trojans or greeks, but even go via L3, on the opposite side of the Sun? Are their orbits circular as Neptune's (in this case) or highly eccentrical? How could an object in the same orbit as Neptune have another orbital period than Neptune? Or how else can it migrate between L3, L4 and L5?

And are "trojan" objects expected to gather in L3 too?

EDIT: 
I'd like to add these illustrations because I think they illustrate well how a regularly orbiting object seems to "stay" longer at L3, L4, L5. (I'm not sure whether "jumping trojans" have some significant other characteristics, though).
In short, most of the trojans stay orbiting arround L4 or L5. These can be called tad-pole orbit asteroids. 

There are some trojan asteroids, however, that their orbit never get's too close to L4 nor L5 to get trapped and have a tad-pole orbit, or they do but they have too much energy to get trapped.

These trojan asteroids have larger orbits, following a path like:

L4 --> L3 --> L5 --> L3 --> L4 and so on. This kind of orbit is called horseshoe.

There is, however, a third kind of trojan asteroid. This one appears to follow a tad-pole orbit (I.E. arround L4), but numerical analysis proves they will eventually adopt a horseshoe-like orbit. When they reach the other stable point (L5) they  will get trapped again in a tad-pole orbit. This kind of orbit is very rare (rarity decreases as planet mass increases) and could be considered (personal opinion) as an hybrid tadpole - horseshoe orbit.

For more information, see:

"Jumping mechanisms of Trojan asteroids in the planar
restricted three- and four-body problems" from: Kenta Oshima and Tomohiro Yanao.