Mark Wilson has just released a Lightroom plug-in Nature Data LR which, at first glance, is about adding to your Library a group of nature-related custom fields:

The fields provide a formal and structured approach to organising your images of natural subjects such as birds and mammals.
The plug-in adds a new metadata panel to the library module, a new dialog to manage the additonal data and an export action to add the data to keywords on exported images.
The plug-in also allows you to create dynamic collections of your photos based on families of species.

I wonder if there's a parallel with geotagging software. What I mean is that I usually can't be bothered to attach my GPS device to my camera, but I'm happy enough dragging the images onto a map when I get home. Equally, if I did get into shooting wildlife, I'd need some help recognising species, something like a dialog displaying whatever characteristics might distinguish a bit-titted wotsit from a striped wotsit, or a male from a female. Maybe that could be pulled from some online reference source, or each creature's record might have hyperlinks?

But wait, there's something else worth noticing:

Naturdata LR makes use of Phil Harvey's excellent ExifTool.

In other words, it's a plug-in with custom metadata and an export feature. This is the aspect of this plug-in that I find particularly intriguing. For one thing it's reassuring that someone other than Jeffrey Friedl has got Exiftool and Lightroom working together - and I hope it shames me into playing with this. But more interesting is what he's doing with it - taking his custom fields and writing them as keywords through the export dialog. As I've written before, just because a program provides hierarchical keywords, it doesn't mean you have to use them, even for something as hierarchical as species..