Life history and Ageing in the wild

The study of why we, and all other living things, progressively deteriorate and become more likely to die as we get older is an issue of relevance to almost every other question in biology. However, the vast majority of ageing research is concerned with mechanistic explanations for declines in function. We have only really scratched the surface in terms of functional explanations for why ageing occurs in the first place, and we are even more in the dark in relation to how ageing proceeds in natural populations. We need to understand ageing in the wild, because it is clear that how ageing works in nature will affect the dynamics of key process such as sexual selection and the evolution of life-histories.

Insects make up the vast majority of animal biodiversity and have been studied intensively in the lab, where they have become important model systems for understanding ageing. However, it seems very likely that when they are taken out of an environment where they have unlimited food and no parasites or predators, insects may show different patterns of senescence. It is now clear that even short lived insects experience senescence on the timescales of their natural life-spans. The importance of insects as laboratory systems for understanding ageing, and the potential for developing a model that can be studied in both field and lab makes understanding ageing in wild insects an exciting prospect. We will carry out a study of senescence in a natural population of field crickets by monitoring the population in great detail. We will DNA fingerprint and tag every individual, and then observe them 24 hrs a day using a network of 160 video cameras. This will enable us to not only measure lifespan and reproduction, but also to collect detailed behavioural information, allowing us to detect what may be quite subtle declines in performance in traits like singing, movement around their burrow, movement over longer distances, mating rate, success in fights with other individuals etc.

By combining the data we will collect during this project with data we have collected over the previous 6-8 years, we will address a series of questions which have been very difficult to answer in the wild because other studies have not had the detailed information that we have:

1. The main evolutionary explanation for ageing is that individuals deteriorate because they pass on more genes by putting all their energy into reproduction early in life even if this takes its toll later in life. We will determine whether individuals that put more effort into early reproduction, for instance by mating more, end up declining faster.

2. We will determine whether environmental conditions affect how rapidly individuals age, and whether years which are more stressful due to climate and competition among individuals are associated with more rapid senescence.

3. Males have been predicted to age faster than females because their reproductive rate isn't capped by how fast they can lay eggs; so they have more potential to evolve to invest heavily in early reproduction even if it kills them. We will see if our males age faster than our females.

4. Females may benefit from mating with old males because their offspring get genes from a male that was able to survive a long time. If males with good genes age slower than males with poorer genes then ageing will make female choice for old males even more beneficial. We will test whether males with other signs of good genes also age slower.

5. It has been suggested that different sources of mortality will have different effects on the evolution of ageing depending on whether they can be avoided by individuals in better condition. We will determine whether the sources of mortality in our population vary in this respect. For instance, whether you get eaten by a robin may simply be a matter for luck, whereas being killed by another cricket may depend on how able you are to defend yourself.

This project investigates fundamental questions about the evolutionary biology of ageing. It is largely curiosity-driven, although clearly the experience of ageing in human populations means that we are contributing to understanding an issue of great significance to most people. To understand ageing properly we will need to understand it in an ecological and evolutionary context, which is the aim of this proposal. In the longer term, this will benefit all those likely to experience ageing.

The study utilises novel video-based monitoring technology which has wide application and potential commercial value. By pioneering new applications of this technology this work will be of direct benefit to the CCTV Industry including both hardware manufacturers and software developers. We have been collaborating with i-code systems (www.icode.co.uk/), who have used our input to substantially develop their software and have sold systems to other academic users in the US and NZ as a direct result of the impact of our work on the development of their product. We expect continued impact of this sort contributing to the economic performance of the UK in this potentially major export market.

We have an established partnership with Ruthern Instruments (based in Bodmin, Cornwall) and have worked with this company to develop an automated multi-channel acoustic monitoring device. The latest version of this device is more flexible and cheaper to manufacture than previous models and Ruthern have now sold several units to other users. We intend to build on this experience to integrate our acoustic monitoring and IP camera system and develop further systems which have commercial potential.

The researcher co-investigator on this project will benefit from acquiring skills across a broad range of areas, including deploying monitoring systems, database design, data analysis etc.
We will ensure that the named PDRA is provided with the opportunity to develop their awareness and skills in knowledge exchange as detailed in our pathways to impact.

The technician on the project will gain new skills in a wide range of areas through their work in analysing video data and collecting data in the field.

The general public will benefit from this research as a result of our planned impact activities: Our study will generate very high quality video recordings of the cricket population studied, and we intend to exploit this resource for the purposes of wider user engagement, with the purpose of providing a high quality learning resource. We have developed a website aimed at the general public which explains the motivations and findings of our cricket-meadow project (www.wildcrickets.org). We will develop this site and associated materials to focus on the use of our system to understand ageing in natural populations, and concepts about selection and trade-offs in life history traits. We will add live video feeds from the meadow, with multiple camera feeds available during the breeding season and a simple web-cam type live overview available year around. We will facilitate public participation in research using a citizen science approach to the task of analysing field cricket behaviour. Using technology to involve people in the research in this way creates beneficiaries; disseminating knowledge about the animals and habitats strengthens understanding of the scientific process and engages people in a deeper way as they feel their effort is valued and contributes to something worthwhile.