Quail Island Biology Trip

Over the last decade the ecologists at Lincoln University have been very involved with the ongoing restoration work on Quail Island in Lyttelton Harbour. Mike Bowie, in particular, has been a major force in keeping the connection going. During this time there have been numerous trips out to the island with dfferent groups of postgraduate and undergraduate students. Over the last week Sue Unsworth. in her role as science outreach co-ordinator, has organised four days of activities on the island involving Year 12 biology high school pupils from the Christchurch and Timaru areas. The students helped in ongoing restoration and conservation projects on the island. They checked tracking tunnels (containing inkpads that leave behind footprints)that monitoring for predators like mice and rats (and luckily found none as there has been a major control operation this year). There were also gull and gull chick counts and lizard lodge (corrugated squares that lizards love to live under) checks for monitoring lizard numbers and species. Despite variable weather and long tiring days, fun was had by all.

Town cats visit the wet rats

Cats are common pets all around the world. Nowhere is this so pronounced as in New Zealand where we have the highest rate of cats/households in the world. One of things that we like about cats is their independence but this comes with a downside - what does your cat do when it is not in the home? Cats are natural predators and we know that they will catch almost any sort of prey. Concerns have been raised that cats may have many negative impacts on local wildlife, especially where their homes are near wild areas. In a study recently published by researchers from Lincoln University (postgraduate students Shelley Morgan, Cara Hansen, and their supervisors James Ross, Shaun Ogilvie and Adrian Paterson) and University of Tennessee (Graham Hickling) in Wildlife Research, this issue was directly addressed. Travis Wetland is entirely surrounded by suburbs in north eastern Christchurch. It is about 120 ha and is the largest freshwater remnant of its type left in Canterbury. As such it has many important natural values and, conveniently, lots of cats live around the periphery. This study surveyed owners around the wetland to find out how many cats were present, what the cats ate, how many were kept indoors for part of the day, and what prey they brought back home. Twenty-one cats were given radio transmitters to examine just where the moggies were going to over a 12 month period. So what did we find out about the secret lives of felines?.

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First, there were a lot of cats - about 600 in the study area or 6.4/ha. Second, the cats didn't mind getting their fur wet. Most cats spent about 10% of their time inside the wetland, moving up to 200 m from the boundary. Of course, being cats, they spent nearly 2/3 of their time at home. Cats moved up to 270 m away from home but usually stayed within 100 m. Male cats had ranges three times larger than females. Almost 1000 prey items were collected during the study with 38% being rodents (mostly mice), 20% birds (almost all introduced birds, like sparrows), 18% reptiles and 22% insects (mainly moths). The bulk of hunting was done by cats from 1 to 6 years of age. Interestingly, cats with bells took more prey (probably because their owners correctly identified them as good hunters). So what does this all mean? Well it is clear that domestic cats do move into nearby 'wild' areas (even those that are quite wet). While there they do kill a great range of species. From a conservation point of view they certainly have an impact on species like native lizards. But of course nothing is that simple. The cats' main prey species are either direct predators (e.g. rodents) or competitors for food (e.g. sparrows) of native species found in the wetland. The question then becomes do the positive outcomes of having cats around, removing problems for native species, outweigh the negative outcomes, killing native species. At this point we can't answer that question. We are currently doing a similar study on cats living around a bush reserve on Banks Peninsula which may tell us more. So overall cats are not the villains they are made out be by some but neither are they as harmless as championed by others.

A successful Banks Peninsula biodiversity workshop

The Banks Peninsula Biodiversity Workshop held at Akaroa on October 8th was a chance for local landowners to learn about the special biodiversity found on their Peninsula properties and what they can do to enhance the habitats for local native species. It was a long and successful day which was attended by over 170 people. Lincoln University and the Banks Peninsula Conservation Trust chose a range of experts to give quality talks on local native fish, invertebrates, birds, lizards, plants and integrating farming with conservation. All of the talks, questions and answers, workshop sessions are being compiled to create a proceedings of the event so that people who attended, and those who couldn’t make it, can read more on the subject. If you did not attend the workshop and would like an electronic copy of the proceedings, contact Mike Bowie.

The Lincoln University/Lincoln Envirotown biodiversity calendar was also launched at the workshop. The calendar suggests ways in which landowners can create or enhance habitats for native species and of course has a lot of spectacular pictures. The calendar is available for only $10. Contact Mike if you would like to buy a copy.

Modelling the invasion

Although the Argentine ant (Linepithema humile) is not the fourth best novelty folk group in New Zealand it is impressively ranked in the top 6 most invasive ant species in the world. In a country like New Zealand this species poses a threat to the local biodiversity by removing native ant species and other prey species and thereby disrupting local ecosystems. Although the ant has established in New Zealand in the Auckland area there is a lot effort spent in trying to stop its spread. In the war against the invasion, knowledge of the future plans of the enemy is valuable in turning the tide. One way of obtaining this information is to create a model which can give us a good idea of where the ant is likely to spread to next so that we can stop this from happening.

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In research just published in Ecological Applications, researchers Joel Pitt and Sue Worner, members of the Lincoln University’s Bio-Protection Research Centre, and their colleague Andrew Suarez from University of Illinois, Urbana, have created models that allow greater accuracy in examining how Argentine ants spread around the landscape. The researchers were frustrated that most existing models only dealt with an abstract environment that was all of one type which helped with the mathematics of the model but was very unrealistic. The team decided to use a GIS approach to include realistic landscape information, such as land cover and local temperature, in their models. A simulation was run for each year from 1990-2005 to look at where the ants would move to and likely survive. What they found was that the simple model assuming a similar landscape was actually quite accurate for the first few years of the invasion. The more complicated model started to perform better after a few years and was reasonably accurate with its predictions when we look at actual spread in 2005 (predicting hotspots of activity in Auckland, Hamilton, Whangerei, Great Barrier Island and Tiri Matangi Island). The figure above shows the areas potentially able to be colonised by 2005 predicted by the simple model (circular lines), the complicated model (colours) and what actually happened (red dots - look closely, they are hard to spot away from Auckland!). The success of this approach will allow managers to better target their resources into monitoring areas that are most likely to be invaded.

Banks Peninsula Biodiversity Workshop

On the 8th October from 9am till 7pm there will be a free workshop held in the Gaiety Theatre in Akaroa about enhancing biodiversity around the Banks Peninsula area. The Banks Peninsula Conservation Trust and Lincoln University have assembled a great line up of contributors for farmers and landowners who want to increase the native biodiversity on their properties. The programme features many speakers which much experience in various aspects of monitoring and enhancing biodiversity. Please contact Rachel Barker (rachel.barker@bpct.org.nz or 03 3296340) to register by the 2nd October.

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Click the picture for a detailed programme of events.

Change under our toes

Grazed tussockland
Originally uploaded by pluckytree

Tussock dominated grasslands are an integral part of New Zealand’s native vegetation. Ecologically, they do not only harbor a large diversity of grasses, shrubs, small woody and herbaceous plants, but also give home to insects, reptiles and birds. Influenced by climatic conditions and land management practices, the spatial distribution of tussock grasslands has varied over time. It is assumed that in the early 1800’s, after Maori fires had cleared much of the forest and before European settlers arrived, they covered about one third of mainland. As of 2002, agricultural land conversion and spreading human settlement have left us with only about 3%.

Today, we are more concerned about “range restoration” and that the preservation of New Zealand’s native landscapes is implemented by adequate land management policies. However, not only has the spatial extent of tussock grasslands declined, but research over the past four decades has revealed ongoing changes in plant diversity and abundance of remaining tussock grasslands, towards an increased dominance of exotic weeds. The reasons for this have never been satisfactorily identified. The degradation has often been blamed on continuous pastoral use of grasslands, but research could never find unambiguous evidence for such a causal connection.

In order to find out more about what was happening in our native grasslands, Lincoln University researcher Richard Duncan and colleagues compared vegetation composition on fixed sample sites in Canterbury and Otago between the mid 1980's and 1990's (see the New Zealand Journal of Ecology, 25(2):35–47). They collected data on a variety of ecological and land management factors to test them for their influence on any observed vegetation changes. As expected, their results after the second measurement did fall in line with prior studies. Native plant species of all families had declined significantly, with the group of small herbs leading the sad trend. On average, one quarter of these plants had disappeared from all measured sites. One notable exception was native grasses of the genus Chionochloa, the snow tussocks, which had obviously benefited from a reduced impact of grazing. The only other significant increase, on the other hand, could be recorded for invasive weeds of the genus Hieracium.

So what had happened? Had the rise of invasive weeds and tall grasses driven out the native plants? Were people to blame, the old culprits, with their grazing livestock and fire management? Were site location and ecological conditions of any importance? To ruin all suspense and excitement right here and now: We don’t really know.

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All statistical analyses run throughout the study could not come up with a significant connection. Native plants did decline on sites with no Chionochloa and Hieracium at all, at the same rate as where these species dominated. Neither did moisture, aspect, increased vegetation cover nor human management play a significant role.

So what had happened? Had the rise of invasive weeds and tall grasses driven out the native plants? Were people to blame, the old culprits, with their grazing livestock and fire management? Were site location and ecological conditions of any importance? To ruin all suspense and excitement right here and now: We don’t really know.

I would like to leave you with a call for continued long-term research into the underlying patterns of our degrading tussock grasslands. Change could be going on independent of human management and so we might have to broaden our research scope and start looking into other factors. Also, the situation may have already changed by now. If towards the good or bad, we can only find out by continued monitoring.

Note that this was the motivation of a recent Lincoln University masters project by Nicola Day. Nicola led the re-surveying of the same plots. Her results will be published soon and we’ll be sure to blog about them here.

This blog post was written by postgraduate student Moritz Wenning as part of the course, Research Methods in Ecology (Ecol608).

Summer Scholarships

The Agriculture and Life Sciences Faculty at Lincoln University, including the Department of Ecology, is offering summer research scholarships over the summer vacation, valued at $5,000 each (tax free). The scholarship will last for 10 weeks. Scholarships will be awarded based on academic merit. So if you want to work on sandy beaches or follow tui around or search for weta in exotic places then have a look at the projects on offer.

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We have run summer scholarships for the last few years and many students have had a lot of fun getting involved with research (and getting paid!). Note that it may say that the due date is the 7th September when it is actually the 14th September.