Yeah, since Japanese kana characters contain a whole syllable, Japanese words will usually take a lot less width than the equivalent English words. And on top of that, they're shortened the words itself as well. In the above example, they actually wrote "Ankylo Desert" and "Stego Hill" instead of the full ~saurus name of the dinosaur.
It'd even be shorter if they used some Kanji instead of only Hiragana for some things like volcano: from かざん to 火山, or Hill: from おか to 岡. (Though I reckon the game resolution may be too low for some complex kanji with a lot of strokes to be clearly legible on a small signboard like the ones above)
I'm sure they could've just lengthened the signboard to accommodate the English characters, but as nat said, they either went the Mario way, or just got lazy. I'd imagine the space shortage issue has got to be a bitch for people who translate games -- especially for fan-translating groups without proper support from the original developers.
Reminds me of playing old school 8-bit RPGs and wondering, why the HELL can I _only_ put in 4 characters for player names? Makes sense now.