Archivos de diario de septiembre 2019

18 de septiembre de 2019

Submitting iNat observations of animal scats/droppings – some suggestions

The ID process – playing detective

It goes something like this: Knowing the size will suggest a series of possible animals (almost never just a single species). The next clue, say that it occurs in a latrine/midden, will suggest a subset of the first list. If the scat contains, say, bones and hair, then a further subset is produced. And so on, until one has some degree of confidence in the final single species ID (if you’re lucky).

In other words, it involves detective work (hence the questions I often bombard observers with). You, the observer, need to look for clues in situ and you need to record as many as possible. Record the clues you observe in (i) your pics and (ii) associated written descriptions.

Consider taking these pics:

(1) The whole deposit or latrine

It should show the overall volume if there’s only one deposit (i.e., the place has only been used once) or the whole latrine/midden if the place has been used many times.

(2) Closeup of the individual pieces with a scale item

The closeup pic should show size, shape, and colour.

Important: Choose a scale item proportional in size to the smallest scat pieces, i.e., a coin or ruler for anything up to some tens of millimetres. A finger is not ideal although it’s better than nothing. You can use your shoe for big stuff like zebra to rhino or elephant. A shoe is useless if they are small scats.

Don’t underestimate the usefulness of an accurate measurement. It can help distinguish, for example, between the various cats, from Black-footed Cat through to Lion. However, each cat’s scat width range overlaps with that of the next smaller and next larger cat. So, unfortunately, this means that, even with an accurate measurement, you may not be able to distinguish between them (when it falls between the average sizes for two cats). Hence, again, the importance of other clues.

(3) Contents, revealed, if necessary, by breaking open the scat with a stick, can provide very useful clues.

(4) Habitat (if you don’t get this in your “whole deposit or latrine” pic)

(5) Other signs of the animal, e.g., spoor, nearby den entrance, diggings, prominence of deposit (on a rock, clump of grass, on rhino droppings, in fork of tree, or buried or partially so).

Observations you could record in your written description:

(1) Any obvious odour.

(2) Anything relevant that you observed but were not able to photograph.

(3) Any information you might have on what animals are known to occur in the area. This is often possible for protected areas which usually have species lists. (Yes, one does need to use such lists with caution.)

Suggest a possible ID (even if it’s just a comment)

Do your best to justify your suggestion. It can help a lot. If you’re uncertain, say so. I have found that sometimes people don’t realise they have useful information (that’s not in their pics or written record).

Join the iNat “Scats & Dung (s Afr)” project

Linking your scat observation to this project will make things more efficient. I monitor this project regularly so I will get your scat pics sooner.

Posted by kevinatbrakputs September 16, 2019 10:27

Tony Rebelo added the following:

Thanks: most useful.
Please join the project here: https://www.inaturalist.org/projects/scats-dung-s-afr

Examples from the project here:
https://www.inaturalist.org/observations?place_id=113055&project_id=scats-dung-s-afr&subview=grid&verifiable=any

to see any particular group just add the taxon into the species box.e.g.
buck - 22 species to date
cats - 5 spp
dogs - 2 spp
rodents - 5 spp
afrotheria - 3 spp
primates - 2 spp
herps - 9 spp
you can even look at a species or subspecies.

Remember if there are Dung Beetles or flies visiting the dung, to please add an interaction to the dung, so that we ca see if some species only visit one type of dung, or many ...

Posted by tonyrebelo 2 days ago

Hail our leading Scatologist! Keep up the kak Kevin - great stuff :-)

Posted by bushboy about 5 hours ago

Ingresado el 18 de septiembre de 2019 por kevinatbrakputs kevinatbrakputs | 3 comentarios | Deja un comentario

20 de septiembre de 2019

A POST-MORTEM … OCCAM’S RAZOR AND A CONTRADICTING PRINCIPLE

This relates to the following observation submitted by @vynbos:

https://www.inaturalist.org/observations/32933634

Let’s use the “spanner” to fix things.

This observation and my own responses to it provide some insights into this challenging business of identifying droppings. I don’t really want to turn this journal facility into a blog, but I think others may benefit from the thoughts below. I have.

MY FIRST MISTAKE

I looked at the pics initially and couldn’t immediately decide whether this was a cat or not (which is why I said initially “while I give this one some thought”). I studied my own published and unpublished cat pics and thought, “well, they could be”.

I saw, and wondered about the substrate, the flattened dry vegetation. “Would a cat do its thing on that?”. It didn’t look right. (This business is a lot about inconclusive feelings, I’m afraid.) A canis species would use such a substrate, I felt.

Then it occurred to me that it was a multiple deposit. A cat producing a multiple deposit?! But the general “rule” is: “they don’t use latrines”. Wow, that’s interesting. And it is just possible, and I gave the (rarely observed) reasons.

What rule did I break you ask? The principle of Occam’s Razor. https://simple.wikipedia.org/wiki/Occam%27s_razor

The principle: If there are two explanations for something, the simplest one is usually correct.

Two possible explanations are:

(1) The multiple deposits (on what seemed an unusual substrate) were possibly a black-footed cat (which is quite scarce) near a den or a wildcat (which rarely does this).
(2) It’s not a cat, but some other carnivore.

Explanation (2) is the simplest.

MY SECOND MISTAKE

I had looked at the map and zoomed in to the best resolution it could give. I even did it in my Google Earth (although the map is the same, GE is more flexible). I noticed the buildings to the south east but made the mistake of not measuring the distance to those buildings. I see now they are only about 500 m away. That should have been at least a red light that a domestic animal could not necessarily be ruled out (whether canis or felis).

I’m still in a bit of that mode in which I have to remind myself frequently that domestic animals are important to consider in this business. (To this end, I included some of them recently in my database of quantitative data, so they appear automatically now. But some refinement is necessary.)
Domestic dogs and especially cats even appear in species lists for some protected areas or are known to have been present but are not recorded in lists.

IN MY DEFENCE (he adds timidly)

Another principle (long used in various other contexts, I see from Google) that I still frequently remind myself of, is this:

“When it concerns animal behaviour, always remember never to use the words always and never.”

[ In the above case, this conveniently negates Occam’s Razor! But let’s not go there. :-) ]

Don’t underestimate this principle. I have seen examples of this over the years. (Just one: Once, and only once, a single unquestionable aardwolf dropping, unburied, on the edge of a dirt road. The “rule” is: They bury them in middens. The lack of adherence to the rule might be easily explained, of course: when you gotta go, you gotta go.)

But, generally speaking, the problem with animals is they don’t read the guidebooks we write about them. If only they would. They might then follow the rules more closely. Our lives would be much simpler.

The only relevance this has to the above-mentioned observation is that one shouldn’t ignore the unusual in this business.

However, I hasten to add, maybe Occam’s Razor should have more prominence than it’s been getting.

Kevin

Ingresado el 20 de septiembre de 2019 por kevinatbrakputs kevinatbrakputs | 0 comentarios | Deja un comentario

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