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The Acorn Connections I Cary Institute of Ecosystem Studies
Page 2 of 3
ln this Project
&*crn C*n*eei!*ns
! inke
Acorns are a key food for white-footed mice. The mice are key predators on Gypsy Moth pupae. When there are
many acorns the mouse population increases, which keeps the moth population low. However if there are no
acorns, the mouse population collapses allowing the moth population to increase. Acorns also attract white-tailed
deer into oak forests to feed on acorns. The deer carry adult ticks that drop off and spend the winter in the oak
forests. The next year the female ticks lay eggs that hatch into larval ticks. The larval ticks are not infected with
the bacteria that cause Lyme disease, but become infected when they feed on the mice that have increased
because of acorns. This means that the risk of Lyme disease can be higher in oak forests two years after a large
acorn crop.
Acorns are a key food for white-footed mice. The mice are key predators on Gypsy Moth pupae. When there are
many acorns the mouse population increases, which keeps the moth population low. However if there are no
acorns, the mouse population collapses allowing the moth population lo increase. Acorns also attract white-tailed
deer into oak forests to feed on acorns. The deer carry adult ticks that drop off and spend the winter in the oak
forests. The next year the female ticks lay eggs that hatch into larval ticks. The larval ticks are not infected with
the bacteria that cause Lyme disease, but become infected when they feed on the mice that have increased
because of acorns. This means that the risk of Lyme disease can be higher in oak forests two years after a large
acorn crop.
Acorns initiate other chain reactions among species (e.9., mice, chipmunks, and songbirds; see R. Ostfeld and
K. Schmidt), and Gypsy Moth defoliation has many effects on the forest, including influences on nutrient cycling
(see G. Lovett). Because moth defoliation reduces acorn production, understanding how moths are able to
persist in the forest amidst intense predation pressure by mice has also been a recent focus of our work. This
has led us to study the roles of local dispersal of moths relative to local spatial variation in mouse predation as
the primary determinants of moth persistence (see B. Goodwin, E. Schauber). Recent research has shown that
there are mouse hot and cold spots in the forest of varying persistence. We are now investigating how these hot
and cold spots affect poths, Lyme risk and songbird nesting success.
Overall, our research is trying to understand how the complexity of interactions among species - including how
they vary in space and time - affects the functioning of oak forest ecosystems wlth important implications for
understanding forest ecosystem health, human health and biodiversity.
Fig. 1. lnteractions in eastern deciduous forests
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nesting songbirds, and gypsy moth dynamics.
Arrows indicate the direction of the ellect of one
taxon on another. Solid lines indicate positive
effects (e.9., mast production on mice), and
dashed arrows indicate negative effects (e.9.,
gypsy moths on oak trees). From Ostfeld &
Jones, ln Press.
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http://www.caryinstitute.org/science-program/research-projects/acorn-connections
LLt3t2012
ilu bric-Acorn Rollercoaster Poster
Due Date:
1. TASK: you are asked to create a poster that will provide the
foJlowing information :
a. Inforrn hikers and other visitors to Virginia's forests the
DANGER YEARS for contracting LYME DISEASE
b. Inform hikers and other visitors to Virginia's forests the YEARS
for peak infestation of gypsy moths
-You are to do so over the 10 year period (1997-2006)
2. Your poster MUST include the following:
a. A LINE GRAPH indicating what happens to EACH population of
organisms in EACH YEAR listed above
b. The graph should include the YEARS along the X-axis and ihe
approximate number of'organisms on the Y-axis.
NOTE: The graph REQUiRES YOU to PREDICT what will happen
based on the information in the article
c. ALL 5 ORGANISMS MUST be plotted on the SAME GRAPH:
1. Deer
2. Gypsy moth
3. Tick
4.
Mice
5. Acorn
NOTE: Be sure to take into account the NUMBER of a specific
type of organism generally found within a population. For
example, there are generally lots more insects in an ecosystem
compared to mammals! (I.E. THINK ABOUT PYRAMID OF
NUM BERSIBIOIVTASS!)
ACORHJ ROLLERCOAsTER
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Learning Experience
4
Population Pressures
Date:
Name:
The Acorn Conneetion
Ecologists: Dr. Ostfeld and Dr. Jones Instituie of Ecosystem
studies, NY
oregon state University,
Biologist: Dr.
wotff
Long term study of gypsy rnoths and the white-foot mouse led
to furtherltudi"r of the interactions within an oak forest and the
su bsequent "acorn connection."
-
"Bumper Crop" means lots of acorns. The oak trees produced
Iots of seeds, i.e. acorns.
.
-oak trees have developed a clever plan for reproduction. what
is it?
.
For-example:
First year: BumPer crop
Acorns rich in Protein and fats
Good seeds for
Favo'i'ite food of
and
.
So, a lot of acorns =
.
Second-Fifth year: poor croP
List results:
.
.
Deer in oak forest import adult ticks. The tick larvae get
dropped
Mouse is a host to
Tick larvae get the microorganism '*spirochete" from the
.
Lu*u. ,olts into nymphs, nymphs molt into adulthood, adult
n
tick gets a ride on the
"
Contact with humans brings about
disease
This study confirms the idea that the deer are the transportation
system for the infected ticks, not the weather, plant life, or any
other factors.
"
Explain how the life cycle of the gypsy moth is connected to the
acorn:
April 16. 1996
Ticks and. Moths, Not Just Oaks, Linked to Acorns
By LES LINE
l
A TANGLED cycle of events in northeastern forests that gives a reason for both Lyme disease
epidemics and outbreaks of glpsy moths has been unraveled by ecologists. They have traced
both events to the bumper crops of acorns that are produced every three or four years and to the
r.vhite-footed mice that feed on tlem.
The bumper acorn crops influence the life cycles of mice and deer as well as the Srpsy moths
and the spirochetes that cause Lyme disease. Based on ttreir theory, the two ecologists, Dr.
Richard S. Ostfeld and Dr. Clive G. Jories of the Institute of Ecosystem Studies in Millbrook,
N.Y., predict that the glpsy moth population in the Northeast will undergo one of its periodic
explosions beginning this year. Theyexpect it to build to a major defoliation in rg99 that will
rival the devastating caterpillarblight of.tg79-8r unless one of the moth's natural enemies, like
a fungus or parasite, intervenes.
The tr,vo ecologists also warn that there will be tremendous numbers of deer tick nyrnphs, the
vectors of Lyme disease, in the oak-dominated woodlands of New York and New England this
spring and summer.
What the two ecologists call "the acorn connection" is laid out in the May issue of the journal
Bioseience in an article written by them and Dr. Jerry O. Wolff, a biologist at Oregon State
University. The study's principal findings come from long-term studies of grpsy moths and
white-footed mice at the Mary Flagler CaryArboretum, site of the Institute of Ecosystem
Studies, and a 14-year studv by Dr. Wolff of mouse populations at the Mountain Lake Biological
Station in southwestern Virginia.
The forests at both sites are dominatedby oaks, which have evolved a cunning strategy for
reproduction- Their acorns are rich in the proteins and fats that give them a head start over
but that also make them a favorite food of mice and deer. So instead of
producing large crops each year, which would foster a steady population of acorn consumers,
the oaks have evolved a feast-and-famine regimen: occasional bumper crops, separated by years
in which the consumers starve.
otler tree
seeds,
"The evolutionary response of oak trees appears to have been to prod.uce such large crops of
acorns that the various forest consumers are simply unable to eat them all, and some survive to
become seedlings," the scientists concluded'
"Trees aren't as stupid as they look," Dr. Ostfeld said'
In the Virginia study, r98o, 1985, rgBB and 1989 were yeals of peak acoln production, while
the
bumper crops were produced at CaryArboretum in r99r and agg4' By regulartrapping,
after a
researchers found that white-footed. mice became most numerous in the summer
or spring'
bumper acorn crop but that their numbers d.ropped sharplythe following winter
Except in bumper years, mice run out of stored acorns by January
the oak-dominated
The next actors in the drama are the white-tailed d.eer, which move into
import a cargo of adult
areas of the forest duringyeals of bumper acorn crops- The deer also
tick larvae, each
ticks, which drop offand lay eggs in the leaf litter beneath the oak trees. The
with a peak
the size of a pinhead, hatch the next summer, just as the woods are overrun
population of their preferred host, t]}e white-footed mouse.
It is from the mice, not the deer, that the ticklarvae pick up the microorganism, called a
meal from the mice,
spirochete, that causes LSrme disease. The ticklarvae take a single blood
tlen molt a few months later'into n1'mphs. The following spring, these Lyme disease-caffjryng
molt to
attach themselves to mice and" other mammals, including humans. They
nymphs
to brush past, and the
become adults in late summer; the adult ticks wait in ambush for a deer
cycle begins anew.
,,Without mice, the deer ticks woutd be a nuisance," Dr. Ostfeld said, "but they would not cause
illness because they hatch from eggs free of the L5'me disease agent'"
have shown that the larvae
By measuring the number of ticks on the forest floor, the ecologists
a bumper acorn crop; they
are most numerous in oak-dominated woods in the year following
that
peakin maple-d,ominated woods in years after poor acorn crops. That confirms the idea
d"". ur" the ticks'principal transport system. "There is no evidence whatsoever that other
said'
factors, particuiarly weather patterns, influence tick abundance," Dr' Ostfeld
woodland rodent with
The spirochetes' special host, the white-footed mouse, is an appealing
the mice measure six to
deer-colored fur, big eyes and big ears; from to the tip of their long tail
another habit that
eight inches. Besides their proclivity for acorns, white-footed mice have
influences the forest: a taste for gypsl moth pupae'
then make cocoons
Glpsy moth caterpiilars feed on oakleaves in the spring and early summer,
said, are "tendel,
and enter a pupal stage for about Mo weeks. The inch-long pupae, Dr. Jones
they will eliminate
tasty morsels,' for the mice. As long as the mice are moderately abundant,
virtually all of the pupae, keeping gypsy moth populations firmly in check.
years of sparse acorn crops, a
But when the mouse numbers suffer their inevitable crashes, in
great many pupae survive ard the moth population builds over tfre next severa-I years, reaching
a peakwhen their hairy caterpillars denude entire hiilsides and damage or kill thousands of
trees. At this point, Dr. Jones said, "you can't get enough mice to contool the moti.s."
The wide-scale defoliation caused,by gypsy moth outbreaks has many influences on the forest
and its creatures. A major impact is on the oala: defoliation may delay or even eliminate the
years of bumper acorn crops. The moths may aiso reshuffle the species composition of the forest
by
killing the oaks, encouraging the growth of saplings from other tree species. "The oak forest
system under study is exceedingly comp1ex," the ecologists said.
Like the soar-and-sink mouse populations, the number of gypsy moths is also prone to sudden
collapse. After caterpillars defoliate many trees, the next caterpillar generation finds that food is
short and that their natural insect and fungus parasites abound- The number of moths dwindles
until conditions are right for their next sugeTo test the idea that white-footed mice keep gypsy moth populations
in eheck, researchers at
Millbrook counted. the numbers of each in successive years. In the summer of 1993, tle mouse
population was moderately high and consumed almost all the S?sy motl pupae within eight
days. But few mice were around the next year, so the pupae could survive uneaten long enough
to hatch into motls
Dr. Robert CoIwelI, professor of ecology and evolutionary biology at the University of
Connecticut in Storrq, said: "This study is-a stunning example of the importance to botl human
and ecosystem health of basic research in ecology and natural history."
of
gpsy
infestations?
far,
it
moth
So
seems not. Supplying exrra
L1,rne disease or the severity of
gypsymoth
feed to the mice in'years of poor acorn crops might minimize
outbreaks, the
ecologists said, butt}.e risk of tickbites would soar. Lyme disease, they said, has already
resulted in "fear and distrust of nature" and has dampened the enthusiasm of many people for
Does this insight into the forest's natural mechanisms suggestways to reduce the incidence
enjoying
tle forests.
Photo: Dr. Clive G. Jones and Dr. Richard S. Osffeld of Institute ofEcosystem Studies in
Millbrook, N.Y., with white-footed mouse and nesting box. (Les Line for The New York Times)
(pS. Cr) Graph/Diagmm: "Of Mice and Trees" shows ttre number of mice found alive on a single
five-acre plot at the Institute of Ecosystem Studies rear Millbrook, N-Y. from 1991to Lgg6.
(Souree: Institute of Ecosystem Studies)(pg- C8 and Cr)
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The Acorn Connections I Cary Institute of Ecosystem Studies
Page 2 of 3
ln this Project
&*crn C*n*eei!*ns
! inke
Acorns are a key food for white-footed mice. The mice are key predators on Gypsy Moth pupae. When there are
many acorns the mouse population increases, which keeps the moth population low. However if there are no
acorns, the mouse population collapses allowing the moth population to increase. Acorns also attract white-tailed
deer into oak forests to feed on acorns. The deer carry adult ticks that drop off and spend the winter in the oak
forests. The next year the female ticks lay eggs that hatch into larval ticks. The larval ticks are not infected with
the bacteria that cause Lyme disease, but become infected when they feed on the mice that have increased
because of acorns. This means that the risk of Lyme disease can be higher in oak forests two years after a large
acorn crop.
Acorns are a key food for white-footed mice. The mice are key predators on Gypsy Moth pupae. When there are
many acorns the mouse population increases, which keeps the moth population low. However if there are no
acorns, the mouse population collapses allowing the moth population lo increase. Acorns also attract white-tailed
deer into oak forests to feed on acorns. The deer carry adult ticks that drop off and spend the winter in the oak
forests. The next year the female ticks lay eggs that hatch into larval ticks. The larval ticks are not infected with
the bacteria that cause Lyme disease, but become infected when they feed on the mice that have increased
because of acorns. This means that the risk of Lyme disease can be higher in oak forests two years after a large
acorn crop.
Acorns initiate other chain reactions among species (e.9., mice, chipmunks, and songbirds; see R. Ostfeld and
K. Schmidt), and Gypsy Moth defoliation has many effects on the forest, including influences on nutrient cycling
(see G. Lovett). Because moth defoliation reduces acorn production, understanding how moths are able to
persist in the forest amidst intense predation pressure by mice has also been a recent focus of our work. This
has led us to study the roles of local dispersal of moths relative to local spatial variation in mouse predation as
the primary determinants of moth persistence (see B. Goodwin, E. Schauber). Recent research has shown that
there are mouse hot and cold spots in the forest of varying persistence. We are now investigating how these hot
and cold spots affect poths, Lyme risk and songbird nesting success.
Overall, our research is trying to understand how the complexity of interactions among species - including how
they vary in space and time - affects the functioning of oak forest ecosystems wlth important implications for
understanding forest ecosystem health, human health and biodiversity.
Fig. 1. lnteractions in eastern deciduous forests
S*e*'
#
*dtq
f*s*rdt
I ny-EY3s
bild*
T L*XITJ
[.X*rre!
Lr
rw**
td& I
{hk,n*sdm
lrr
, t{t *
x
1+
ll
\
*lisrffi
Iffk*l
g*J I
\L*
i
-Ttcl*
r*
\
ary I .-J
t
w ,f}J
nesting songbirds, and gypsy moth dynamics.
Arrows indicate the direction of the ellect of one
taxon on another. Solid lines indicate positive
effects (e.9., mast production on mice), and
dashed arrows indicate negative effects (e.9.,
gypsy moths on oak trees). From Ostfeld &
Jones, ln Press.
B*a
fd**4*w
tc; ntr rP*sBur ffii
1
*t*
i
{ { {:
I unc*nt*,y
{
! *#*p
influencing forest dynamics, Lyme-disease risk
("pathogens"), nesting success of some ground-
fi&x Tmffiffi*
{*
,TJ
{
% -&
http://www.caryinstitute.org/science-program/research-projects/acorn-connections
LLt3t2012