NON-NATIVE LAND VERTEBRATES

People ner.11 t o bcrome more aware o jp rohfcms caused by ,yIicti ~,cnebrores in narurul areas in ikuivai i. They musr cilso rcnhze tha t something can and shou ld be done,

Charles P. Stone

Vertebrates (anin~ols with hackhones) includs mammals, hirds, reptiles, amphibians, and fishes. Recause Harai ' l is located soma 1,500 nii (4,000 km) froni continents, some oi these groups are not well rcpresentcd by specie5 thar arrived without the help of humans. Hauai'i has no native amph~hisn\ or lard reptiles. and onlv one land ~imnrnnl (the Hawaiian or h o : q b~t (La~iunrc cinereus), 'upe'up,,'~), six specie? of native nun-marlnc fishes. and 57 s p c k s of native land hirds. Yet natursli+ed (hwing estahlishcd populations) 5pecicl of vertchrate. ~includinr Poltncsian introducrionil incluc!:. 19 mammal>. 45 birds, and I? reptilesvand amphibians.

I N I T I A L INTRODUCTIONS BY MAN

With the initial arrival of Polynesian people in ahout 400 A.D., vertehrate introductions began. The early settlers deliheratel brought what is generally considered the Polynesian triad--pig, dog, and chic i; en (Sus scrofa, Canis familiaris, Ga1lu.s gallus). But they also brought some stowaways--the Poly- nesian rat (Ratfirs erulans) and some re~ t i l e s keckos and skinksl Most of the 5 crrehcires introducr;l by l 'o lynesih delGnded on hur imsand prohahly did not seriously in\;ide nmve ecosystems. Thc! Ilkel!, frequented llawaiian setrlements m d clld not do as much darnnge UI the n;,tive biota ar tlie nctiviries of Pol!ncian humans (clearing l o ~ l ; ~ ~ i d fore\[. killing flight- l e u hirds, selling i:res, and so forth). 'fhz rat w y have been an eweprion. as elwvherc i t is known tc)r.at rhc eggs of seabirds. S~udies in Hawai'i ha\e shown that it was prohnbly quite a threat 1 0 flighkcs insects and ground- dwelling mails. Rut until Ca t i n James Cook arr~ved in 1778, thr introtliiced vertehrate most harmful to tk'c'nntlve biota u a j ~ rohsh ly the hunim a n i n d , rather than the species that arrived with him.

THE SECOND PHASE-THE HOOFED M A M M A L S

The arrival of Captain Cook and other sea captains shortly thereafter inaugurated a second group of vertehrate introductions. Animals that would be useful to future visitors and which were appreciated by the Hawaiians were brought ashore. These included cattle, goats, European pigs, sheep, and

horses (Bos IUUIUS. Cauru hircus. Sus scrofa. OviE mie.s. Ermr~r caballus). The .. - - . - 7 ~ ~ - - - -~ - ~awai ians favored these ipecies so much that ~ l l & ~ ~ l : ~ r e d a knpu (tahoo) on many of hem, allowing numhers 111 huild up tremendously. AS a result, native pl?ni community structure and cpmposition deteriorated in forests where the nnmals fed. Unlike the Polmeslan introductions. these animals became feral ~~, ~ ~ ~ ~ - . ..-~..~. (dqmestic animals no longei dependent on man) over much of Hawai'i. Fe- ralizahon was helped, of course, by increasing exploration bv man, clearing of forests, and settlement bv immigrants. LaFlre numhers ofintroduced hoofed mammals (ungulates) ate pal:rt:~hie native plants, rctluced p l a ~ t ~ o p & t i o ~ s , and caussd the c.\tinctions of numerow plant \ p e w s unadspted to hrowsiny. gazing, trampling, and erosion.

- But more than olants were destroved. Native birds and invertebrates

(such as insects nndland mall,), depsndent on the hahitat providcd bythe plant?. were also reduced. Opening oi the forei~s by the feral nngulates albo changed normal light, moisture, m ~ d nutrient cvcling pattern.. For c w n ~ l c . in some areas drahaee natterns of water were ilter&l because there was'lit-' . .~ ~

tle native veget:,tion'ird to catch rain or to hold soil. Soils c&np:~cred by ~~

animal hooves favored rapid r ~ r o f f ofwater. As P . ~ I I I S fronl elsewhere in the world were :ntrodu;cd to 1iou.ai'i. hoo id marnm:lls crested ~ l a c e r Isvnrabk for them in native ecosvsterns hy rcmovine natlve plant,. Un&~tes distribu- ted alien plant seeds c!~riging to their hair and carrlcd in thc~r digesrive tracts. Alrm ~lnn tz iurttrer altered n;lti\.e ~lar i l succession bee Smith. Non- Native Plants: this volume). ~ ~

By the 1i,ic~~~i800s. foresters arrd nthera in Haw4i.i had beconie concerned ahout the destruction of watersheds (area? which amtrihute to cctmmon water collection and runoff downslone) caused bv feral uneulates. A oroeram to reduce ungulate pupula~ions k l make run'ofi patte&s morc c&si$cnt and water less turhid (muddy) eventuallv resulted. I t included the planting of introduced s~cc ies of trees, creation and fencing of Forest Resenes, removal of animals through huntin ' and poisoning, and bounty system (payment for evidence of animals killedf. This p/rilosoph of ungulate reduction to protect watersheds and soil continued untd 1959, w 1 en responsibility for feral ungu- lates was transferred from the Hawai'i Department of Agriculture to the Hawai'i Department of Land and Natural Resources (DLNR). At this time, hunting seasons and hag limits for ungulates were established and !he p,hilosophy became one of sustained yield management (perpetuation of con- sistent numbers of animals) for hunting, rather than reduction of animals to protect ecosystems and watersheds.

THE THIRD PHASE -- SJIALL MAJIMAIS, BIRDS, AND AIORE UNGULATES

Black Rats and Mon ooses In the late 1800s an d into the mid 1900s. transportation, settlement, and

visitation to the Islands continued to increpse. The black rat (Ruthls ratha) probably arrived by accident some!tme between 1870 and 1890 in Hawai'i and began to severely impact natlve blrds and probably mollusks). 6 The last Laysan rails (Ponanulapalmen) were era lcated on Midway Islands, as was a population of the Laysan finch (Telespyza cantans). Other species, especially colonial-nesting seabirds, were updoubtedly also easy prey for black rats, and predation on tree-nesting birds such as Hawaim

mosquitoes, may have reduced native bird populations prior to the arrival of malaria.

Un dates %roblems caused by cattle, pigs, and goats were aggravated by the inuo-

duction of additional hoofed anlmals. Although sheep had been ~ntroduced by Vancouver in the 179k, sheep-raising began in the late 1800s. Once feral cattle were controlled, feral sheep became a serious problem in mamane (Sophora chysopltylla) forests of Mauoa Kea, for example. A court order to remove the sheep from the mountain was issued in 1979 to protect the Endan- geredpalila (Loxinides bailleui), and most feral sheep are now gone in the - Gpperelevations.

Axis deer (Rrir mis) were introduced to the island of MolokaT in 1868 and became a pest within 30 years (Tomicb 1986). They were also released on Maui and Lana'i, where they inhabit private lands, and they are now managed hv the State for hunting on Moloka'i and Lana'i. A nonulation in Moanalua

~~~~~~

valley on O..~hu u m r&md or clim1n8ted hy deveiol;ment, predation hy doer, and ponshins. hlm:lon sIicr.ii (OIL! r n u s i ~ w ~ ~ j uere released on Lana'i in 19.54 and are st81 hunted there. Releases on Mauna Kea on Hawai'i Island

~~ ~

have hvhrid~zcd t t l \onlr. J c i r ~ , c wi th icral h c p . M~,ufl~in are now heing removed f r m i tlauna Kea fur thc \:me rcswnt feral ,hcep previouslv were . . removed.

THE FOI'KTH 11H:4SF.-- CONTINL'IN(; I'KOI{LERIS

Increasing resident human populations, especiallv on the outer islands (from s n 0 jli~ [)c~r~pectivc~. i ~ i l ~ i , t ~ . anJ touiim hive ~ntensified the mro- d~ction and yirrsd a!f dien ; ~ n i n i ; t l ~ 111 Il:an:~~'i. Opening and fragmentation of the feu reni:~irii~~~! ~ ~ : ~ : u r i t l :are;,. 111mn\ that nlien animals have more oouor- tunitv to oenetrate :reas which once were resistant to them. Smaller and' ' , , more irregular ar~.:l. haw more edge jun..tions of different vegetation types) for alien snimalc ro c m t x t n;~tive tore\[.

Animal invaswm d!en includc an irruotive oeriod when Iarne numbers of aliens survive and increase in numbers. A jlopulHtion of much l&er numbers usuallyfollows the peak and persists at that level. During the peak, the effecti on native ofev s~ec ie io r ~ l an t s can be ereat and even result in their extinction. ~ach'ne& a'nim:d in&i~in can ha\*;effects on different native species in a natural area at peak po[rulxion levels, and eventually many sbecies of native olants and-animdican become rare or extinct i s a result of siuccessivc alien i;ruptions. ([:or cxarnplr, common myna, (Acndolheres trirrk), although not resident in native forests now, once were abundant in them in their ~rnmtive phase i n the IXWs. The harmful effects of omnivorous myna% on forest plants ind anim;ds were probably great for a short period and may have done lasting damage in forests.)

Introduced wecies of venehrates such as the domestic eat (Fdis catus). often released dc'lihcrately in natural areas, and the house mouse ( M u s d o k - fim) are now widcsliread in Hawai'i and undoubtedly have more effects on native soecies thin we know. In contrast to the moneoose. the feral cat hunts at niiht and i\ ahle to prey on roosting or nestinglbirds when the are r most vulnerahlc. Also in contrast to the mongoose. cats are readily ah e to

climb trees to atrnck oirds. Mcc are abundant enough to reduce significantly the numbers of cceds produced hy some native plants, thus inhibiting produc- tion of voune ~lants . Mice also serve as an im~ortant and consistenifbod hase fo; SII& ipecles as mongonres, cats, and ham owls, thus supporting Ii~cher number\ of species nhrch prev on n a h c vertcbratcs than ~ t ~ u l d <ither- . . wiie be possible. -

Populations of some introduced species may still be expanding in numbers and distribution. Mongooses reach higher population dens~ties on Caribbean islands than they have reached on simdar-sized Hawaiian islands. Feral pigs have invaded areas like Kipahulu Valley on Maui since the 1950s. and the bogs in u per Hana Rain Forest and new areas in the West Maui Mountains as recent P v as the 1980s. The reasons for this are not well understood. but in some csses. mutitalistic relationchips with introduced pl:ints may rerult in llicreased densities and di~~ributions of b u ~ h p i y anJ plsnts. Introduced :~nimxls (sttch as r l u s and earthworms) mav also favor increaced densities and distribution of pigs. -Adjustments in rai popidations may still be in progress, with black rats becoming more abundant than Polynesian rats in some areas for unknown.reasons. It is possible that these situations may not represent long-term trends as much as shifting advantages resulting from climatic patterns or other factors, but significant damage to the native biota may occur either way.

The introduction of new species of vertebrates to Hawai'i is a constant threat. In 1987, two brown tree snakes Buga meguluk) from Guam were f. ' ' discovered in Honolulu and destroyed ( Engbring, personal communication). This species is responsible for elimination of nearly all of the forest bird species on Guam \Savidge 1987). An Animal Species Advisory Committee and an Aquatic Li e and Wildhfe Advisory Commission for each Hawai'i countv are charged with reviewine deliberate im~ortations of new s~ecies. Ilowever, the clkncer of ilccidenhl intrducti rn's and of rnovcmenis o i species from place to place within 1l;iwai'i arc gre:it (rec Smitl~, Controlline the Flow. . . ithis volume).

-

MANAGING INTRODUCED VERTEBRATES

There are five hsically different objectives in managing introduced icrtelirateh in 1I:wdi'i. TI:ey are: 1) Su\tsined \ield; 2) I:'rad:cati,~n: 3) Long-term population reduction; 4) Short-term population reduction; 5 ) Natural regulation.

The Hawai'i Department of Land and Natural Resources vractices sus- [:liner1 vielJ man:igekenr for feral ungul:~tes and gnme birds oh moct StnK properly. The ltitent 1s to hunt anim;~ls only t t ~ the point \r herc p~~pulzunn levels can be maintained for future hunting. An exceotion is Stateland on 113una Kes, whcre thc mmagcment goal For i d h e e p and mouilor. i. no\% cradicntion to protect palila h3hitat.

On lands on ned hv the Nblionbl Park Senice snd 1 h e Yarurc Con3cr- van? of Hawaii, the goal for feral ungulate management is kmg-term reduc- tit~n or era.lica!ion tu prorsct native sco\!.ten~>. Er:,di~:ttror~ L I S U ~ I I V rc- quires fencing of areas to seuamte them from outside area, for which other ~3nagcme~it-ohjccti\cs have been e'tablibhed, or 10 crexte rnme niann<eablc areas within which animals can be eradicated. Re(luctton or eradicmon rrith- i n fences i, hy hunting uith rifles (go:tts): hunting nith dugs (pigs): or sn:~rin$.

tr:lppit~g, ;lnJ h~~nti:lg i n c~mhir~;~r ion (pig<). \lun:torin(: o f ; ~ n i n ~ s l p ~ ~ p u l s - tion, I11 d c t e r n ~ : ~ ~ e sI:ttu, Jur~n,: w m r d snd cradicjti~tn progrunic olid cnllccr~n; of d:11:1 from atlini;tls ;I\ the! arc rcmo\ed are ~nip~rt; lnt s t t p 111

dcterminin~. the Cit 'Cai\~llc~\ t l iprt l&m\ and i n iniproving their r.iiiilr.n.y. Slonitoring u i \,egetatiorl resow!. i \ a lw useful. Counting the numhcr of :mimaI\ rcmovcd mitv m:.n little, ~ L I I i n i h n m o n on thc rate OI' rcn1ov;t. ner unit area is im~oi tan t '

Short-trrm r e d u i t d ia u\usll) the i~h iec r i~c in rn;rnagemcnt of man- I or I . Ihe h ~ r h popl.l;diun dr~i>itlr.\. widespread tli\tr~hutions. and r 3 ~ l d r e ~ r o d ~ ~ c t i v c rate, t ~ f t k \ c m;J tnan1111:1li make r.r:tdic;lrion or lonu- te;ni rcductiort ~~xtrenicl) ~tnlikrl,. )'el, reducing n~~rnhers i n import:lnt nLrll- ral arm\ prlctr 10 or during hreeJing ~ e : w n ~ for cndsngercd bird,. or during vulnerable fruiting or seeding periods for native plants,may be possible. Aii anticoagulant poison called diphacinone is being developed in Hawai'i to reduce mongoose numbers in breeding areasused by eight Endangered bird s~ecies . Testing the effectiveness of oredator reduction on the survival of $ung birds hasnot yet been atternpied, and we do not yet know the best tlmes for and intervals between treatments with diphacinone.

Research on t r amins anticoamlants. and acute toxicants for black rats

determined. Short-term reduction of some alien bird populations in some high-value areas ma] also be possible, but this has not been attempted in Hawai'i. For example, mynas are social birds and may be subject to decoy tramine. in which a few birds lure others into tram. Reduction of kalii ph&& (Lopl~ura leucornelanu) by shooting or'trapping may be pos$ble and is desirable to reduce dispersion of the alien vine banana poka (Passiflora mollissirnu) in some areas.

aeement ohiective. The numbers of ~ i g s . alien birds. fats. insects. and so

humans can alleviate some of the neeative effects of alien vertebrates on the - n:ltiw hiold 111 < t m c > I ~ I I ; ~ ~ ~ I I I I A . InJccd, 11 can hc argued th:,r, iinie human. in~ti.t~ecl ~ I I C problem.; either kt~~i\in&,d! or unknoisingly i n the fir31 {11;~e. we have vnne rcm~n>il~il i tv to elimin:~te then1 where othcr value5 are ~mvur tan~ . In any event, tb allow natural regulation to result in high numbers of aliens is really "management by default." Management,of introduced species by nat- ural regulation or sustained yield to "non-damagmg" levels in ecosystems where they have not evolved is "biologically meaningless" (Gagnk 1988). Rare and vulnerable native species and ecosystems are put at risk by lack of human concern and action.

FUTURE NEEDS AND RECOMMENDATIONS

Considerable information is available for managing hoofed animals.

native ecosystems need attention, especially on Natural Arca Reserves and some other conservation lands owned by the State.

The feasibility of short-term reductton of mongooses, rats, and alien birds still requires research. However, reduction of human disturbances (roads, trails, housing developments, food sources, and so forth) in native ecosystems, and less fragmentation of remaining natural areas, will result in fewer alien bird species and lower numbers of alien birds there (Scott et al. 1986).

Education of the general public, teachers, and important decision-makers in political and business communities is critical. People need to become more aware of problems caused by alien vertebrates in natural areas in Hawai'i. They must also realize that something a n and should be done. A minimum is to avoid introducing alien vertebrates to new ~ laces . There is a need to out

ting io long-term action programs for natural areas are given elsewhere in this volume and in the literature (see especially Myers 1986).

Important References

Bergcr, A.J. 1974. History of exotic birds in Hawaii. 'Elqaio 35(6):60-65. Berger, A.J. 1975. History of exotic birds in Hawaii. 'Elepuio 35(7):72-79. Gagnb, W.C. 1988. Conservation priorities in Hawaiian natural systcms. Bioscience

38(4):264-271. Juvik, J.O., and S.P. Juvik. 1984. Mauna Kea and the myth of mulliple use: endangered

species and mountain management in Hawaii. Mo~omirt Research orid Developrurrtt 4191-202.

Moulton. M.P.. and S.L. Pimm. 1983. The introduccd Hawaiian avifauna: biaeeoeraohic u - .

evidcnce far competilion. American Nonmlist 121(5):669-6!M Moullan, M.P., and S.L. Pimm. 1986. Species introductions to Hawaii. Pp. 231-249 IN H.A.

, , Springer-Verlag, New York.

Myers, N. 1986. Tockii,~Mr?ss &ti,,& of Snccies: A Great Crpotiw Cilallerqe Horace M. ~ l b r i g h < ~ c c t u r e s h i ~ in C&s&atian 26. Univ. California, ~ e r k c l c ~ .

Savidge, J.A. 1987. Extinction of an island forest avifauna by an introduccd snake. Ecology 68(3):660~668.

Scott, J.M., S. Mountainspring, F.L. Ramsey, and C.B. Kepler. 1986. Forex1 Bird Co,mmnities of tile Howuiim Islands: 771cir Dymmics, Ecology, m d Consewotion. Studics in Avian Biology 9. Cooper Ornithological Socicty, Berkeley, California.

Smith, C.W. [this volume] Controlling thc flow of non-native species. Smith, C.W. [this volume] Non-native plants. Stone, C.P. 1985. Alien animals in Hawai'i's nativc ecosystems: toward conlrolling the

adverse effects of introduccd vertebrates. Pp. 251-297 IN C.P. Stone and J.M. Scott (eds.), Howois!r TemsIn'oI Eco~yxfms: Pwswwlion and M a n o p t e m . Unir. Hawaii Press for Univ. Hawaii Cooperative National Park Resources Studies Unit, Honolulu.

Stone, C.P., and J.O. Keith. 1987. Control of feial ungulates and small mammals in Hawaii's national parks: research and management. Pp. 277-287 IN C.G.J. Richards and J.Y. Ku (eds.), Conlrol of Momn~olPests. Supplcrnent 1, Tropical Pest Management 32. Taylor and Francis, Ltd., London.

Stone, C.P., and L.L. Loope. 1988. Reducing impacts of introduced animals on native biota of Hawai'i: what is being done, what needs doing, and the role of national parks. Envimntnental Conservation 14(3):245-254.

stone, C.P., and J.M. Scott (eds.). 1985. HawoiS's TerreslrialEcovStems: Preservation nndManogemen1. Univ. Hawaii Press for Univ. Hawaii Cooperative National Park Resources Studies Unit, Honolulu.

Tornich, P.Q. 19%. Mon~mals in Hawaii: A Syftopsis and NotorionnlBib,iograPhy. 2nd edition. Bishop Museum Special Publ. 76. Bishop press, ~~,,,,l~l,,.

van Riper, S.G., and C. van Riper, 111. 1982. A Field Guide to flte Mamntols in Howoii. The Oriental Publ. Co., Honolulu.

Vitousck, P.M., L.L. Loope, and C.P. Stone. 1987. Introduced species in Hawaii: biological effects and opportunities for ccolagical research. Trends in Eco/omondEvoltrtion 2(7):224-227.