Thursday, 23 July 2015

Dung roaming: a controversial approach to cleaning up New Zealand's cattle waste

Although I've already discussed the dangers of using biological control in various countries, a couple of recent events suggested I should write an update that concentrates on one particular example in New Zealand. I've mentioned elsewhere that my local reserve in Auckland is home to a large number of non-native species, from Australian eucalyptus trees and the associated (but accidentally imported) Emperor Gum moth, to California quail and Mexican gambusia fish. But having seen rainbow skink in my local environs, including a neighbour's garden, I was surprised to learn last week they are not native but yet another unplanned Australian import. Sure enough, the 1947 classic Powell's Native Animals of New Zealand makes no mention of the species in the page on the indigenous common skink and copper skink.

Earlier this year I read Quinn Berentson's superb Moa: the life and death of New Zealand's legendary bird, which lists fifty-eight avian species as having become extinct since humans first arrived in the country less than a thousand years ago. And of course this decimation of native fauna and flora may not yet have ended, with NIWA for example fighting a rear guard action against unwanted marine incomers such as polychaete worms arriving on ship's hulls and in discharged ballast water. Various sources suggest that well over one hundred introduced species of land animals, birds and fish are now widespread in New Zealand: what chance does the native ecosystem stand against this onslaught?

To add insult to injury, I recently read an OECD chart delineating business spend on research and development as a percentage of GDP, and was shocked to find that New Zealand was fourth from bottom of twenty-six nations, coming below western Europe, South Korea, Japan, Australia, Canada and the USA. Are our captains of industry really so short-sighted? As a country that depends extremely heavily on its dairy industry - an industry that is currently in dire straits - it seems sensible to invest a large amount of R&D in this sector. But alongside the eco-friendly solutions such as minimising methane emissions, there has been a new programme of biological control aimed at one particular side effect of dairy farming, namely the enormous amounts of cattle dung produced.

Across the Tasman, Australia has already been working on a similar scheme for the past half century, deliberately introducing numerous species of non-native dung beetles. New Zealand, home to over ten million cattle in a 3:2 dairy-to-meat ratio, obviously has issues with bovine manure management. Due to the lack of native ruminants the country's fifteen indigenous dung beetle species have evolved to mostly inhabit forests rather than grazing land.

There are various reasons why speeding up the rate of dung decomposition would improve farm land and the landscape in general, from preventing mineral imbalance in the soil and contamination of waterways to reduction in animal-infesting parasites such as nematode worms. But is it worth the risk to the greater environment, considering the dismal track record of biological control schemes around the world?

The new project is not the first time such insects have arrived in the country: in addition to three species accidentally imported from Australia and South Africa from the late Nineteenth Century onwards, the Mexican dung beetle (Copris incertus) was deliberately introduced into three areas in the 1950s but only thrived in the warm Northland climate. It is the scale of the new research that has set it apart: following caged field trials, the past two years has seen the widespread introduction of eleven non-native species across seven regions on both North and South Islands.

Bodies such as the Institute of Environmental Science and Research (ESR) have investigated the potential dangers to human health and the local ecology, even testing if possums, carriers of bovine tuberculosis, might see the exotic insects as a new food source. Even so, some professional scientists have deemed it a biosecurity disaster and one can see their point: using data from other countries' programmes is hardly a fool-proof comparison, considering the profoundly different indigenous ecosystems of Australia and New Zealand.

As a child I heard about the food chain or pyramid, but this is something of a misnomer. Just as natural selection works with bushes rather than linear progression, so there are food webs consisting of a complex series of trophic interactions. Although exotic dung beetles are unlikely to displace their native counterparts due to lack of shared environments, it is possible that other native species of grassland-living insects could suffer, such as humble earthworms. The problem is that without testing in various regions over long periods of time, it isn't viable to rule out such side consequences. Yet it isn't possible to undertake such tests without release into the wild: do we have something of a catch-22?

Having said that, there are no obvious signs that Australia's long-established dung beetle programme has had anything like the deleterious effects of its other biological control schemes, such as the cane toad fiasco. But then fifty years is a very short time in ecological timeframes and what to the casual glance of a farmer appears to be equilibrium could be apocalyptic at dung beetle scale. I wish the project good luck, but cannot help feeling that having received far more than its fair share of obnoxious aliens, New Zealand is the last place that needs yet more exotic species introduced onto its green and pleasant land.

Wednesday, 24 June 2015

Sea monkeys: easy care pets or cheap lab animals?

As a former keeper of shield or tadpole shrimp (species Triops longicaudatus) in the UK, I miss the little blighters here in New Zealand, where they are banned as a biohazard. Although there is a rare native species, Lepidurus apus is apparently not suitable for keeping in household tanks; has anyone ever tried, I'd like to know?

Anyway, about four years ago I was looking for an alternative critter when I remembered someone at a party once mentioning sea monkeys, a hybrid species of brine shrimp suitable for keeping at home. Artemia nyos are very cheap to purchase and look after, with little in the way of paraphernalia required to keep them alive. (Incidentally, in addition to not being monkeys - obviously - they also don't live in the sea; the parent species are native to saline lakes.)

The most noticeable difference for me after Triops is that they don't require the frequent water changes that tadpole shrimp do. What's more they live somewhat longer: I've managed lifespans over six months, compared to just half that for Triops. In addition, sea monkeys can live in tiny tanks and so are the ultimate in pint-sized pets - or to be more accurate, three-quarters of a pint-sized pets.

Being only half the size of Triops, they require close-up observation; even with a themed tank, you are unlikely to get anything like a tropical aquarium experience. What's more, they refrain from digging motions and the other more interesting traits found in tadpole shrimp, mostly swimming on their backs, mating, or fanning through particles at the bottom of the tank for food. In fact, apart from some aquabatics, sea monkeys don't appear to have an awful lot to offer. For example, they don't have the range of behaviour that I've observed in individual tadpole shrimp, such as exuberant laps or hiding behind objects in the tank. Once you've observed them for a few months, the novelty begins to wear off, especially when they start dying in droves.

Therefore I thought that they might offer some interesting opportunities for scientific research with the minimum of apparatus. I initially tried a few changes - such as keeping a spotlight on at night during the first week of a new tank, partially for the warmth - but this was too informal to count as good research. I then started keeping a diary of the tanks, leading to a series of experiments aimed at finding the optimal conditions for maximising both number of individuals and longevity. I can't say that after three years' of research I have exactly found the brine shrimp equivalent of the elixir of youth but I've certainly enjoyed playing biologist, even if my methodology and laboratory conditions aren't quite up to professional standard (insert smiley here if you like).

Towards the end of the research period I explored some websites where other owners/breeders/keepers (delete as appropriate) had also experimented on the animals and their eggs. These raised some interesting questions, including concerns over the amoral nature of some practical science. Even so, it all gave me a good opportunity for to write this post!

For those without sea monkey experience, here's a brief summary of what is involved in their upkeep:
  • A commercial water conditioner is added to a 12 ounce/350ml tank containing non-chlorinated (in my case, bottled) water, although the conditioner sachet often appears to include some eggs.
  • A separate sachet of eggs is added a day or so later. The eggs usually hatch between two and five days after this, the water temperature directly correlating to the speed of hatching.
  • Some days after hatching, the shrimp begin to be fed miniscule amounts of powdered algae, the frequency depending on the number of adults.
  • The water level is topped up once every month or so with bottled water.
  • Ideally, the tank is aerated every one or two days, in my case using an 'aqua leash' included with one of the tank kits.
Sea monkey with eggs

So a fairly simple care regimen, then. None of my tanks have ever had more than seven adults at a time, which contrasts markedly with the congested tanks I've seen in internet videos. Whether it is the absence of light at night or cooler temperatures in general compared to other owners I'm not sure, but the lack of numbers was certainly not through a shortage of aeration or appropriate amounts of food, except during several months' of experiments as described in this summary of my research:

Q1: Could I raise sea monkeys using a ratio of water conditioner to water 30% lower than recommended?
A1: Negative. No eggs hatched. (See, I'm trying to use the correct scientific tone...)

Q2: Could I raise them using a tank substrate?
A2: Not wanting to waste eggs and conditioner I only performed this once, using finely crushed sea shells thoroughly rinsed in bottled water. No eggs hatched.

Q3: Did the brand of bottled water (with differing amounts of dissolved solids) make any difference to hatching numbers or longevity?
A3: Not noticeably.

Q4: Did a mature, mixed female-male population produce more hatchlings than a female-only population?
A4: Marginally, although after the initial hatching once a tank was set up, very few later nauplii survived more than a month.

Q5: Were, as I had read, the shrimp more photo-reactive when the tank was crossed by narrow beams of light in an otherwise dark environment?
A5: I saw very little evidence for this.

Q6: Did the distance from a window and direction/angle of daylight affect numbers?
A6: This was tricky, since around ninety minutes on a sunny window sill was all I allowed in order to prevent a tank transforming into a serving of Bisque du mer singe. But there was little evidence to suggest the amount of light altered the number or longevity of the population.

Q7: Did the tank temperature affect hatching numbers?
A7: I didn't want to use a normal tank thermometer, the tanks being so small, so I only had the fairly inaccurate sort that stick on the outside of aquaria. The only correlation I saw was that on colder nights it was better to keep tanks away from the window sill where it was obviously chillier than elsewhere in the room.

Q8: Did the frequency of aeration affect the population?
A8: I tried various permutations, from twice daily, to three times per week, to just once a week or even less, but this appeared to make little difference. Then again, I wasn't successful in raising more than five nauplii in any one 'mature' tank at a time, and so perhaps the population was too low to require greater oxygenation.

Q9: Did the feeding frequency affect the population?
A9: Again, I tried a range of schedules over several years, from once every five days to once per month. However, the low adult populations meant there was never any danger of starvation: their digestive tracts always looked full and at various times, individuals were accompanied by long strings of excrement. Hmm, nice!

Q10: Could I raise sea monkeys using a homemade water conditioner?
A10: This was the last experiment I undertook. I scoured the internet for the correct quantities of ingredients before trying several sea salt and baking soda ratios, but no eggs hatched after a month.

Head of a sea monkey

After I had completed these experiments, I searched the internet and found that my methods were rather tame compared to some of the research conducted on sea monkeys, and indeed brine shrimp species in general. Therefore here are some other potential experiments for those with the inclination:
  1. Try other foods, such as baker's yeast
  2. Try rain water or using self-created distilled water
  3. Conduct water quality tests (aquarium kits such as for the ammonia/nitrate/nitrite cycle)
  4. Egg hardiness, such as freezing and microwaving before attempting to hatch them*
  5. Different oxygenation techniques, such as blowing (not exhaling) a fresh intake of air through a straw.
*I'm too squeamish for this sort of thing. Does it make me a poor amateur biologist? After all, it's not as if I'm looking to cure diseases or any other really useful addition to humanity's knowledge; it's just some interesting minutiae on small invertebrates. Not worth putting them through it, really!

Although they are claimed to be easy to raise - indeed, other species are used for toxicity testing and their eggs subjected to cosmic ray experiments - I don't seem to have had much luck with breeding large populations (or in a rather more scientific tone, the condition of my tanks has proved to be sub-optimal). When one adult died, most of the other adults usually followed within a week. Despite frequent matings, lasting hours or even days and repeated several times per week, I've never seen more than five nauplii hatch in the same week in a mature tank. In addition, most seem to die after the first few instars, with very few reaching maturity. On the other hand, I once saw a tank with fully-grown shrimp belonging to a child who had added food daily but never aerated. Despite the water being obscured by thick algal growths, a few individuals managed to hang on in a presumably very oxygen-poor environment. Yet my zealous attention has seemingly had little impact!

So whilst they don't live up to the cuddliness of say guinea pigs, they are extremely useful as err...experimental guinea pigs, as it were, for the amateur biologist. And yes, watching the aquabatics can be fun, too!