Our feline friends - not so miaowvellous after all?

I've published a few posts concerning citizen science, from the active participation in conservation-orientated projects here in New Zealand to the more passive involvement in distributed computing projects that I briefly mentioned back in 2012.

A type of public involvement in scientific research half way between these examples has been developed to utilise the human ability to match up patterns, a skill which artificial intelligence is only just beginning to replicate. One early implementation of this was the Galaxy Zoo crowdsourced project, in which volunteers examining photographs taken by robotic, Earth-based telescopes to classify galaxies. Since 2009, the Zooniverse online portal has utilised more than one million volunteers to examine data on behalf of over fifty projects, many of which are within STEM disciplines.

Although initially often used for astronomy or astrophysics programmes, crowd sourcing platforms have latterly found an important role in conservation and biodiversity research. An example is the Smithsonian Institute-sponsored eMammal, which specialises in the examination of camera trap footage to identify the locations of animal species on a scale that could not obtained by other means.

In line with the outcome of the perhaps too ambitious Predator-free 2050 programme, one project that may require the assistance of the Zooniverse volunteers is analysis of feral cat DNA from New Zealand's Auckland Island. The DNA, derived partially from fecal matter (nice), is to discover what the cats on the island are eating. Although this research aims to discover the best way to remove invasive species from Auckland Island (cats are known to predate on native seabird species) there now appears to be another issue caused by cats living near coastlines.

Over the past fifteen years a body of evidence from around the world has shown that cats are directly responsible for the deaths of marine mammals. This might sound rather unlikely, but the microbial culprit, Toxoplasma gondii, is only found in the digestive system of cats. Both feral and domestic cats that catch and eat infected rodents or birds can acquire the parasite and pass it by their fecal matter into the wider environment via fresh water run-off or sewage outfalls. Eventually, it enters the marine food chain, reaching the apex in the former of cetaceans and pinnipeds among others.

Species such as sea otters, seals, and dolphins have been killed by toxoplasmosis, according to autopsies of specimens washed up on seashores as far apart as New Zealand and the USA. Increasing temperatures (thanks again, man-made climate change) and greater rainfall can spread toxoplasmosis even further. In addition to direct contamination from fecal matter, cat owners who flush cat litter down the toilet can also start the highly resilient microbes on a journey via sewer networks to the ocean. Among the New Zealand species proven to have been killed by infection are the critically endangered Maui dolphin and locally vulnerable Hector’s dolphin, so there is definitely a need for some prompt action.

It isn't just a case of the top marine predators eating infected fish or squid: sea mammals could swallow oocysts (basically, the protozoan equivalent of a fertilised egg) directly from water. Only now that Maui dolphins are falling victim to the parasite is the story of this deadly microbe becoming better known. Not incidentally, our species can also become ill with toxoplasmosis due to exposure to cat feces, with serious consequences for babies born to infected mothers and to people with compromised immune systems. In addition to the other potential dangers from the likes of Salmonella, Listeria and E. coli, the recent fad for 'raw' (i.e. unpasteurised) milk could lead to a far higher rate of toxoplasmosis in humans.

What can be done? Well, cat owners could stop flushing kitty litter down their toilets for a start. Is it a case that there are just too many cats in the world? Some recent reports claim that Homo sapiens and their domesticated species constitute 96% of the global mammal biomass. As for cat numbers, an estimate last year suggested that there are six hundred million pet cats and the same number of feral individuals worldwide.

Is this just too many? I admit that I'm fairly biased as it is: a few cat owners I know here in Auckland have pets that regularly kill skinks and it's only luck that these are invasive rainbow skinks rather than rare native species. When it comes to the likes of the last 55 Maui dolphins falling prey to a disease spread by an extremely common domesticated species, I'd rather be over-zealous than over-cautious in developing a solution. As far as I can see, the best control methods would be a vast reduction in cat numbers or the development of an innoculation for our feline friends that can kill the parasite. Somehow I doubt either course of action is likely, which means a far from purrfect method would be to educate cat owners as to how to minimise the spread of Toxoplasma gondii. So if you are a cat owner, or know of one, I guess this could be your time to shine...

Backyard bonanza: collating stats for a predator-free future

I've previously discussed how a lack of understanding of statistics can cause consumers to make poor choices, so it would seem that increasing the public's understanding of them can only be a good thing. Therefore, along the lines of New Zealand's annual garden bird survey, I decided to do a bit of citizen science. My aim was to record the highest number of each fauna species seen at one time, either actually in my garden or seen from my garden. The time frame was a calendar year, so as to take into account seasonal migrations and food availability. As an aside, it might have been easier to count flora (after all, it doesn't move very fast) but with Auckland being the weediest city in the world and my floral knowledge much weaker than my recognition of fauna, I opted for the easier option of any animal that I could see without using a microscope.

A meta-analysis released this month states that almost twenty-five percent of birds on the IUCN Red List of Threatened Species are being affected by climate change. In addition, with last years' announcement to make New Zealand predator-free by 2050, such surveys might be useful for locating concentrations of introduced pest species. In a way, I'm providing a guide that anyone can follow with the minimum of effort (hint, hint). So here are my results, followed by some more information:

Class/species	Native/self-introduced	Number seen
Insecta
Ant (unknown species)	Yes	Numerous
Asian paper wasp	No	3
Black field cricket	Yes	4
Bumble bee	No	1
Bush cockroach	Yes	14
Cabbage tree moth	Yes	7
Cabbage white butterfly	No	2
Cicada	Yes	2
Click beetle	Yes	2
Common bag moth	Yes	1
Crane fly	Yes	1
European earwig	No	1
Ground beetle	Yes	2
Honey bee	No	1
Housefly	No	7
Ladybird	Yes	2
Monarch butterfly	Yes	17
Shield bug	Yes	3
South African praying mantis	No	22
Tree weta	Yes	18
Arachnida
Bird dropping spider	Yes	1
Black cobweb spider	Yes	1
Black house spider	Yes	1
Daddy long-legs	Yes	3
Jumping spider	Yes	1
Nurseryweb spider	Yes	1
Slater spider	Yes	1
White tail spider	No	1
Annelida
Earthworm	No	5
Tiger worm	No	Numerous
Hexapoda
Springtail	No	Numerous
Chilopoda
Centipede	Yes	3
Mollusca
Common garden snail	No	9
Reptilia
Rainbow skink	No	2
Aves
Australasian hawk	Yes	1
Blackbird	No	2
Black headed gull	Yes	3
Eastern rosella	No	4
Fantail	Yes	2
Goldfinch	No	3
Greenfinch	No	2
House sparrow	No	14
Myna bird	No	4
Rock pigeon	No	5
Silvereye	Yes	7
Song thrush	No	1
Spotted dove	No	1
Starling	No	4
Tui	Yes	1
Mammalia
Cat	No	2
Chicken	No	1
Dog	No	1
Hedgehog	No	1
Mouse	No	1
Rabbit	No	1

The first thing that seems obvious is just how many non-native species I observed, some deliberate introductions whilst others accidentally brought to New Zealand, but all within the past two centuries.

Now for some interesting comments about how statistics can be (mis)interpreted:

1) The method I chose to order the table by could affect how easy it is to find key points of interest. Alphabetical order is familiar but is simply a well-known form of cataloging. Therefore it can be seen as a neutral form of presentation, not emphasising any particular pattern of the results. Had I ordered by native/non-native, it might have become more apparent how many of the latter bird species there are. If I had ordered all species in one list by this method, rather than in separate classes, the pattern would have been obscured again. So simply by selecting a certain order, results can appear to support a certain notion.

2) How useful is this data if it lacks supporting information? By this, I mean factors that might affect the count: Is it a common or garden (yes, that's a pun) location or an highly unusual one? Is the locale urban or rural? What are the surroundings? How big is the garden and how much vegetation is there? Is the vegetation primarily native or non-native? I could go on like for this ages, but clearly to get a more sophisticated understanding of the causes behind the figures, this information is necessary. Even then, two locations that are almost identical to a casual observer might appear profoundly different from the vantage point of say, earthworms. I will admit to (a) having built 2 weta motels and a bug motel; and (b) feeding silvereyes in winter; and (c) having made a tui sugar water feeder that has been totally ignored. Go figure!

3) Are there any other obvious factors that could affect wildlife? How managed is the location? Are chemicals such as weedkiller used or is the garden solely organic? Again, this can have a massive effect on wildlife, such as pesticides that remove insects at the base of food webs. On the one hand, if mine is an organic garden surrounding by neighbours who spray their foliage, then it could be an island of suitability in a comparatively barren terrain. But alternatively, if most of the neighbourhood isn't fauna-friendly, how likely would my garden get visited even on the off-chance by animals that can't live in the wider area?

4) Of course there's also contingency within natural selection. For example, quite by chance some species can survive on foods not native to their ecosystem. Although stick insect numbers in New Zealand were drastically reduced thanks to DDT, gardens don't need to contain their native food plants in order to support them. In the south-west of England, three species of accidentally-introduced New Zealand stick insect have flourished for decades on the likes of roses! Also, unusual events can affect populations: in this case, the two rainbow skinks appeared several months' after laying some ready lawn so I can only assume their eggs arrived with the turf, the previous five years having seen no skinks whatsoever.

5) When it comes to surveys, timing is also important. As you might expect, most of my observations took place during the day, with the only nocturnal ventures being on clear nights when using my telescope. The moths and hedgehogs were mostly seen at night, whilst had I included birds I could hear as well as see, then a morepork would have been added to the list. Again a simple prejudice, in this case sight over sound, has skewed the statistics. The large number of mantises were not adults but nymphs all hatching from a single ootheca. As for the monarch butterflies, they were a combination of caterpillars, chrysalis and adults, having appeared in much greater numbers this year than previous, despite no additional swan plants (their only food). Interesting, a clump of twenty or so mature swan plants a few streets away hasn't yielded any monarchs in any of the three stages. Presumably, predators such as wasps are responsible.

The sheer randomness of nature is exciting, but doesn't exactly help to uncover why populations are such as they are found via small-scale studies. Oh, and further to the damage invasive species have wrought on native wildlife, you may be interested to learn that none of the mammals belonged to me, the cats and dog being owned by friends and neighbours whilst the rabbit was an escapee from a dozen houses away!

6) Finally, there's the scale prejudice. Although I have a basic microscope, I didn't include such tiny wonders as tardigrades and bdelloid rotifers, even though garden moss and leaf litter respectively has revealed these wee critters. My page of nature photographs shows this prejudice, with microscopic fauna getting their own page.

So, what can we learn from this, apart from the large number of non-native species commonly found in Auckland? Perhaps that raw data can be presented in ways to obscure patterns or suggest others, should the publisher have an agenda. Furthermore, without access to highly detailed meta data, the statistics by themselves tell only a small part of the story and as such are open to wide-ranging interpretation by the reader. Therefore the next time you read about some percentage or other, remember that even without manipulation or omission, survey data is not necessarily pure, unsullied and free of bias.