Invasive species

Overview of Feral and Managed Honeybees in Australia

Distribution, Abundance, Extent of Interactions with Native Biota, Evidence of Impacts and Future Research
David C Paton, Department of Zoology, The University of Adelaide
for Australian Nature Conservation Agency
Environment Australia, May 1996
ISBN 0 6422 1381 X

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Contents

Foreword

The impact of introduced species on native populations is usually assumed to be negative, but as you will see from this overview, feral honeybees can produce both positive and negative effects on native plants and animals. In this report it is shown that feral honeybees can enhance the seed production of a number of native plants whose native pollinators have declined substantially due to a variety of factors. It has also shown that feral honeybees can reduce the seed production of other native plants and compete with honeyeaters for nectar.

These varying effects on the native environment show that it is important to quantify the impact of feral animals on native species before any management decisions are made. It may be beneficial to leave the system as is if introduced animals are compensating for a decline in native species. However, if the impact is determined to be negative to the natural environment, then strategic control operations and appropriate management strategies are justified.

This series of national overviews was commissioned by the Invasive Species Program to comprehensively assess the information, available on a range of introduced species and serves to highlight key gaps in our knowledge. I trust that this series of overviews will be a useful tool when considering future research to enhance our knowledge base.

[signed]

Peter Bridgewater
Chief Executive Officer
Australian Nature Conservation Agency

Summary

Feral and managed colonies of honeybees have been present in Australia for about 170 years, but their distribution and abundance has increased dramatically over the last 60 years. There are over 500,000 managed hives in Australia and an unknown number of feral colonies. Managed colonies are patchily distributed in time and space, with beekeepers usually shifting loads of around 100 hives into and out of areas for 2-4 month periods coinciding with peaks in flowering of key plants (often species of Eucalyptus). A concentration of 100 hives at the site of an apiary is only equivalent to about 0.1 colonies per hectare, because honeybees forage out to distances of at least 2 km from their hives, covering at least 12 km².

Feral colonies are also patchily distributed being least abundant, if not absent, from alpine areas and inland areas away from water. Limited quantitative data show densities ranging from 0.001 feral colonies per hectare in inland mallee-heaths to locally high densities of 0.77 colonies per hectare in riparian woodlands. Locally high densities, however, may reflect restricted availability of suitable hollows and not effective densities in the area as a whole.

The hollows used by feral honeybees broadly overlap with those used by a variety of native birds and mammals, but feral colonies appear to occupy only a small proportion of the available hollows (often < I%). This suggests that interactions between feral colonies and hollow-nesting Australian fauna may not be substantial but few studies have adequately assessed the availability of suitable hollows, particularly their internal characteristics.

Honeybees visit the flowers of at least 200 Australian plant genera and interact with a wide diversity of native flower-visiting animals. For many plants, honeybees were the most frequent floral visitors, and often consumed more than half of the floral resources' being produced.

Numbers of native bees may decline following influxes of honeybees into an area but data on this relationship were equivocal. Reproductive performances of several species of native bee also did not change dramatically following influxes of honeybees to areas. However, honeybee densities may not have been manipulated adequately to cause a measurable response, and second order interactions involving responses by predators or parasites may have disguised the responses of native bees.

Responses of honeyeaters to influxes of honeybees varied. In Banksia ornata heathlands where there was a surplus of floral resources the numbers of honeyeaters did not change following influxes of honeybees, but at patches of Callistemon rugulosus New Holland Honeyeaters increased the sizes of their feeding territories and reduced the frequency with which flowers were visited. Population densities in patches of Callistemon were reduced by 30-50% when honeybees were prominent.

Honeybees also influenced the production of seeds by various plants. At some plants seed production was reduced when honeybees were frequent floral visitors (eg C. rugulosus) while at others seed production was enhanced (eg B. ornata). Plant species whose seed production increased were those that received inadequate attention from their native pollinators. Plantpollinator systems are vulnerable to perturbations like habitat clearance and degradation, and some Australian plants may now depend on honeybees for full pollination because their native pollinators have declined dramatically or even disappeared in some areas.

Whether honeybees should be included or excluded from selected areas will depend on which native taxa are to be favoured in those areas. Some plants may benefit by the presence of honeybees while other plants and animals may continue to suffer degradation in their presence.

Future research should measure the effects of honeybees on a wide diversity of native flora and flowervisiting fauna to firmly establish the extent of detrimental interactions. Both descriptive and experimental studies are needed. The spatial and temporal scales of manipulative experiments must be carefully considered. Manipulations that reduce rather than increase the numbers of honeybees working flowers in an area may be more relevant to future management programs that are likely to reduce the numbers of honeybees in an area. Some priority should also be given to studies on the population dynamics of feral colonies of honeybees and broadacre methods of efficiently removing feral colonies from selected areas.

Management of honeybees in areas set aside for conservation will remain contentious while there is insufficient information about interactions between honeybees and the Australian biota. A regional approach that leads to at least some of the natural resources within each region being maintained free from honeybees would promote conservation of regional biodiversity and provide an alternative management strategy that is not reliant on measuring the effects of honeybees on natural systems. Ultimately effective management of honeybees and natural resources will depend on cooperation from the beekeeping industry.

Disclaimer

Funding to compile this report was provided by the Australian Nature Conservation Agency (ANCA) under the Invasive Species Program. The views expressed in this report are not necessarily those of ANCA.

Acknowledgements

Numerous people have assisted in the development of this overview. I thank Leigh Ahern, Graham Arnold, Phil Arming, Jim Armstrong, Harold Ayton, Tad Bartareau, David Bell, Fred Benecke, Andrew Bennett, Lindsay Best, Alan Anderson, Lee Allan, Linton Briggs, Tom Burton, Tim Clancy, Geoff Cotton, Jason Crouther, Paula Dewar, Leigh Duffield, George and Jennifer Ettershank, Mike Fleming, Hugh Ford, Bill Freeland, Caroline Gross, Tim Heard, Steven Hopper, Michael Hornitsky, Gavin Jamieson, Graham Kleinschmidt, Kay Lambert, Susan Lawler, David Lindenmayer, Richard Loyn, Rob Manning, Eric Matthews, Mike Moncur, Neville Munns, Ben Oldroyd, Graham Pyke, David Rounsevell, Michael Schwarz, Owen Seeman, Alan Spessa, Ken and Deane Spurge, Evan Sugden, Vivienne Turner, Helen Wallace, Bryan Walsh, Tony Wapshere, Ray Wills, Geoff Williams, Karen Williams, David Woodward, Alen Yen and Karen Ziegler for responding to my requests for information on honeybees and management of natural resources. I thank Leigh Ahern, Jim Armstrong, Tad Bartareau, Robert Begg, Caroline Gross, Loraine Jansen, Graham Kleinschmidt, Susan Lawler, Rob Manning, David Rounsevell, Steven Smith, Alan Spessa, Evan Sugden, Vivienne Turner, Bryan Walsh, Tony Wapshere, Nick Waser and Ray Wills for providing many constructive comments on a draft of this report. Kathie Stove assisted with correspondence and editing. I thank Jim Barrett, David Carter and Andrew McNee for their patience and support in the production of this report.

Cover of Bounceback - Flinders Ranges - Brochure

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